Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Thu, Jul 16, 2020 at 9:21 AM Brent Roose  wrote:

> Hey Nikita
>
> Thanks for the rebase. I just tested this on one of our most largest
> projects (after verifying that the warning does show in a dummy test case),
> and all is fine. So from my point of view, there is a theoretical chance of
> breaking code, but I believe this won't have a large impact, at least not
> on modern-day projects.
>
> Kind regards
> Brent
>

Great to hear, thanks for testing!

Regards,
Nikita

On 15 Jul 2020, at 11:10, Nikita Popov  wrote:
>
> On Wed, Jul 15, 2020 at 10:56 AM Brent Roose  wrote:
>
> Hi Nikita
>
> Yes that would be nice, if it's not too much of a hassle. I'm only able to
> test this in one or two large Laravel projects, so it would still be a
> limited test.
>
> Kind regards
> Brent
>
>
> Done! https://github.com/php/php-src/pull/3917 is now based on current 7.4
> HEAD. Note that it just unconditionally throws a warning, without a way to
> disable it.
>
> Nikita
>
> On 15 Jul 2020, at 10:53, Nikita Popov  wrote:
>
> On Wed, Jul 15, 2020 at 10:49 AM Brent Roose  wrote:
>
> Hi Nikita
>
> Is the ini setting available in current 7.4 builds? Is it documented
> somewhere? I'd like to test this change in some of our projects.
>
>
> We did not introduce an ini setting in PHP 7.4, I only used it for my own
> experiments. The implementation is available at
> https://github.com/php/php-src/pull/3917. I could rebase that to current
> 7.4 if that would be useful.
>
> Nikita
>
> On 15 Jul 2020, at 10:28, Nikita Popov  wrote:
>
> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson 
>
> wrote:
>
> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
>
> On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov 
>
> wrote:
>
>
> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov 
>
> wrote:
>
>
> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>
>
> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
> wrote:
>
> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It
> doesn't
> have to be. I think that type juggling comparisons in a language like
> PHP
> have some merit, it's just that the particular semantics of == in PHP
> make
> it so dangerous. The biggest WTF factor is probably that 0 ==
>
> "foobar"
>
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics
>
> of ==
>
> and other non-strict comparisons, when used between a number and a
> string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> The tl;dr is that if you compare a number and a numeric string,
>
> they'll
>
> be
> compared as numbers. Otherwise, the number is converted into a string
> and
> they'll be compared as strings.
>
> This is a very significant change -- not so much because the actual
>
> BC
>
> breakage is expected to be particularly large, but because it is a
> silent
> change in core language semantics, which makes it hard to determine
> whether
> or not code is affected by the change. There are things we can do
>
> about
>
> this, for example the RFC suggests that we might want to have a
> transition
> mode where we perform the comparison using both the old and the new
> semantics and warn if the result differs.
>
> I think we should give serious consideration to making such a change.
> I'd
> be interested to hear whether other people think this is worthwhile,
>
> and
>
> how we could go about doing it, while minimizing breakage.
>
> I generally like the direction and think we should seriously consider
>
> it.
>
>
> I think that before we make any decisions on this, or even dive too
>
> deep
>
> into the discussion - we actually need to implement this behavior,
> including the proposed INI setting you mentioned we might add in 7.4
>
> - and
>
> see what happens in some real world apps, at least in terms of
>
> potential
>
> danger (as you say, figuring out whether there's actual breakage would
> require a full audit of every potentially problematic sample.
>
> Ultimately,
>
> I think there's no question that if we were to start from scratch,
>
> we'd be
>
> going for something along these lines.  But since we're not starting
>
> from
>
> scratch - scoping the level of breakage is key here.
>
> Zeev
>
> Totally agree that assessing the amount of breakage in real code is key
> here. I have now implemented a warning for PHP 7.4 (for now
>
> unconditional,
>
> no ini setting) that is thrown whenever the result of a comparison is
>
> going
>
> to change under the currently proposed rules:
> https://github.com/php/php-src/pull/3917
>
> I've done a few initial tests by running this against the Laravel,
> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
>
> times
>
> for Symfony and 2 times for pear-core. (See PR for the results.)
>
> Both of the warnings in pear-core pointed to implementation bugs. The
> Symfony warning was due to trailing whitespace not being allowed in
>
> numeric
>
> strings (something we should definitely change). One of the Laravel
> warnings is ultimately a false-positi

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Wed, Jul 15, 2020 at 5:12 PM Arnold Daniels 
wrote:

> Hi Nikita,
>
> One of the problems with numeric string comparisons is that it might
> interpret a hexadecimal value as scientific notation
>
> $red = '99';
> $purple = '9900e2';
> $red == $purple; // true
>
> I suggest only interpreting a number formatted with a sign ("1e+100") or
> with decimals ("1.0e100") as scientific notation as part of this RFC. These
> are the notations that languages use when casting a float to a string,
> never "1e100"
>
> PHP "1.0E+100"
> JavaScript "1e+100"
> Python "1e+100"
> Ruby "1.0e+100"
> Java "1.0E100"
>
> Arnold
>

Hey Arnold,

I don't want to include this change in this RFC (because the proposal does
not otherwise touch string-to-string comparison at all), but I do think
this is a very good idea. I was not aware of this particular variant of the
issue (i.e., that it also occurs with prefixes other than "0e") and this
seems like a pragmatic way to resolve that particular ambiguity. A question
here would be whether to make this something specific to string-to-string
comparisons, or make a general change to numeric string recognition (i.e.,
no longer treat "1e100" as a numeric string, only "1.0e100" or "1e+100".)

Regards,
Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Brent Roose]

Hey Nikita

Thanks for the rebase. I just tested this on one of our most largest projects 
(after verifying that the warning does show in a dummy test case), and all is 
fine. So from my point of view, there is a theoretical chance of breaking code, 
but I believe this won't have a large impact, at least not on modern-day 
projects.

Kind regards
Brent

> On 15 Jul 2020, at 11:10, Nikita Popov  wrote:
> 
> On Wed, Jul 15, 2020 at 10:56 AM Brent Roose  > wrote:
> 
>> Hi Nikita
>> 
>> Yes that would be nice, if it's not too much of a hassle. I'm only able to
>> test this in one or two large Laravel projects, so it would still be a
>> limited test.
>> 
>> Kind regards
>> Brent
>> 
> 
> Done! https://github.com/php/php-src/pull/3917 
>  is now based on current 7.4
> HEAD. Note that it just unconditionally throws a warning, without a way to
> disable it.
> 
> Nikita
> 
>> On 15 Jul 2020, at 10:53, Nikita Popov > > wrote:
>> 
>> On Wed, Jul 15, 2020 at 10:49 AM Brent Roose > > wrote:
>> 
>>> Hi Nikita
>>> 
>>> Is the ini setting available in current 7.4 builds? Is it documented
>>> somewhere? I'd like to test this change in some of our projects.
>>> 
>> 
>> We did not introduce an ini setting in PHP 7.4, I only used it for my own
>> experiments. The implementation is available at
>> https://github.com/php/php-src/pull/3917 
>> . I could rebase that to current
>> 7.4 if that would be useful.
>> 
>> Nikita
>> 
>>> On 15 Jul 2020, at 10:28, Nikita Popov >> > wrote:
>>> 
>>> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson >> 
 
>>> wrote:
>>> 
>>> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
>>> 
>>> On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov >> >
>>> 
>>> wrote:
>>> 
>>> 
>>> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov >> >
>>> 
>>> wrote:
>>> 
>>> 
>>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski >> > wrote:
>>> 
>>> 
>>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov >> >
>>> wrote:
>>> 
>>> Hi internals,
>>> 
>>> I think it is well known that == in PHP is a pretty big footgun. It
>>> doesn't
>>> have to be. I think that type juggling comparisons in a language like
>>> PHP
>>> have some merit, it's just that the particular semantics of == in PHP
>>> make
>>> it so dangerous. The biggest WTF factor is probably that 0 ==
>>> 
>>> "foobar"
>>> 
>>> returns true.
>>> 
>>> I'd like to bring forward an RFC for PHP 8 to change the semantics
>>> 
>>> of ==
>>> 
>>> and other non-strict comparisons, when used between a number and a
>>> string:
>>> 
>>> https://wiki.php.net/rfc/string_to_number_comparison 
>>> 
>>> 
>>> The tl;dr is that if you compare a number and a numeric string,
>>> 
>>> they'll
>>> 
>>> be
>>> compared as numbers. Otherwise, the number is converted into a string
>>> and
>>> they'll be compared as strings.
>>> 
>>> This is a very significant change -- not so much because the actual
>>> 
>>> BC
>>> 
>>> breakage is expected to be particularly large, but because it is a
>>> silent
>>> change in core language semantics, which makes it hard to determine
>>> whether
>>> or not code is affected by the change. There are things we can do
>>> 
>>> about
>>> 
>>> this, for example the RFC suggests that we might want to have a
>>> transition
>>> mode where we perform the comparison using both the old and the new
>>> semantics and warn if the result differs.
>>> 
>>> I think we should give serious consideration to making such a change.
>>> I'd
>>> be interested to hear whether other people think this is worthwhile,
>>> 
>>> and
>>> 
>>> how we could go about doing it, while minimizing breakage.
>>> 
>>> I generally like the direction and think we should seriously consider
>>> 
>>> it.
>>> 
>>> 
>>> I think that before we make any decisions on this, or even dive too
>>> 
>>> deep
>>> 
>>> into the discussion - we actually need to implement this behavior,
>>> including the proposed INI setting you mentioned we might add in 7.4
>>> 
>>> - and
>>> 
>>> see what happens in some real world apps, at least in terms of
>>> 
>>> potential
>>> 
>>> danger (as you say, figuring out whether there's actual breakage would
>>> require a full audit of every potentially problematic sample.
>>> 
>>> Ultimately,
>>> 
>>> I think there's no question that if we were to start from scratch,
>>> 
>>> we'd be
>>> 
>>> going for something along these lines.  But since we're not starting
>>> 
>>> from
>>> 
>>> scratch - scoping the level of breakage is key here.
>>> 
>>> Zeev
>>> 
>>> Totally agree that assessing the amount of breakage in real code is key
>>> here. I have now implemented a warning for PHP 7.4 (for now
>>> 
>>> unconditional,
>>> 
>>> n

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Arnold Daniels]

Hi Nikita,

One of the problems with numeric string comparisons is that it might
interpret a hexadecimal value as scientific notation

$red = '99';
$purple = '9900e2';
$red == $purple; // true

I suggest only interpreting a number formatted with a sign ("1e+100") or
with decimals ("1.0e100") as scientific notation as part of this RFC. These
are the notations that languages use when casting a float to a string,
never "1e100"

PHP "1.0E+100"
JavaScript "1e+100"
Python "1e+100"
Ruby "1.0e+100"
Java "1.0E100"

Arnold

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Wed, Jul 15, 2020 at 10:56 AM Brent Roose  wrote:

> Hi Nikita
>
> Yes that would be nice, if it's not too much of a hassle. I'm only able to
> test this in one or two large Laravel projects, so it would still be a
> limited test.
>
> Kind regards
> Brent
>

Done! https://github.com/php/php-src/pull/3917 is now based on current 7.4
HEAD. Note that it just unconditionally throws a warning, without a way to
disable it.

Nikita

> On 15 Jul 2020, at 10:53, Nikita Popov  wrote:
>
> On Wed, Jul 15, 2020 at 10:49 AM Brent Roose  wrote:
>
>> Hi Nikita
>>
>> Is the ini setting available in current 7.4 builds? Is it documented
>> somewhere? I'd like to test this change in some of our projects.
>>
>
> We did not introduce an ini setting in PHP 7.4, I only used it for my own
> experiments. The implementation is available at
> https://github.com/php/php-src/pull/3917. I could rebase that to current
> 7.4 if that would be useful.
>
> Nikita
>
>> On 15 Jul 2020, at 10:28, Nikita Popov  wrote:
>>
>> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson > >
>> wrote:
>>
>> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
>>
>> On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov 
>>
>> wrote:
>>
>>
>> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov 
>>
>> wrote:
>>
>>
>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>>
>>
>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>> wrote:
>>
>> Hi internals,
>>
>> I think it is well known that == in PHP is a pretty big footgun. It
>> doesn't
>> have to be. I think that type juggling comparisons in a language like
>> PHP
>> have some merit, it's just that the particular semantics of == in PHP
>> make
>> it so dangerous. The biggest WTF factor is probably that 0 ==
>>
>> "foobar"
>>
>> returns true.
>>
>> I'd like to bring forward an RFC for PHP 8 to change the semantics
>>
>> of ==
>>
>> and other non-strict comparisons, when used between a number and a
>> string:
>>
>> https://wiki.php.net/rfc/string_to_number_comparison
>>
>> The tl;dr is that if you compare a number and a numeric string,
>>
>> they'll
>>
>> be
>> compared as numbers. Otherwise, the number is converted into a string
>> and
>> they'll be compared as strings.
>>
>> This is a very significant change -- not so much because the actual
>>
>> BC
>>
>> breakage is expected to be particularly large, but because it is a
>> silent
>> change in core language semantics, which makes it hard to determine
>> whether
>> or not code is affected by the change. There are things we can do
>>
>> about
>>
>> this, for example the RFC suggests that we might want to have a
>> transition
>> mode where we perform the comparison using both the old and the new
>> semantics and warn if the result differs.
>>
>> I think we should give serious consideration to making such a change.
>> I'd
>> be interested to hear whether other people think this is worthwhile,
>>
>> and
>>
>> how we could go about doing it, while minimizing breakage.
>>
>> I generally like the direction and think we should seriously consider
>>
>> it.
>>
>>
>> I think that before we make any decisions on this, or even dive too
>>
>> deep
>>
>> into the discussion - we actually need to implement this behavior,
>> including the proposed INI setting you mentioned we might add in 7.4
>>
>> - and
>>
>> see what happens in some real world apps, at least in terms of
>>
>> potential
>>
>> danger (as you say, figuring out whether there's actual breakage would
>> require a full audit of every potentially problematic sample.
>>
>> Ultimately,
>>
>> I think there's no question that if we were to start from scratch,
>>
>> we'd be
>>
>> going for something along these lines.  But since we're not starting
>>
>> from
>>
>> scratch - scoping the level of breakage is key here.
>>
>> Zeev
>>
>> Totally agree that assessing the amount of breakage in real code is key
>> here. I have now implemented a warning for PHP 7.4 (for now
>>
>> unconditional,
>>
>> no ini setting) that is thrown whenever the result of a comparison is
>>
>> going
>>
>> to change under the currently proposed rules:
>> https://github.com/php/php-src/pull/3917
>>
>> I've done a few initial tests by running this against the Laravel,
>> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
>>
>> times
>>
>> for Symfony and 2 times for pear-core. (See PR for the results.)
>>
>> Both of the warnings in pear-core pointed to implementation bugs. The
>> Symfony warning was due to trailing whitespace not being allowed in
>>
>> numeric
>>
>> strings (something we should definitely change). One of the Laravel
>> warnings is ultimately a false-positive (does not change behavior),
>>
>> though
>>
>> code could be improved to avoid it. I wasn't able to tell whether the
>>
>> other
>>
>> one is problematic, as it affects sorting order.
>>
>> I have to say that this is a lot less warnings than I expected. Makes
>>
>> me
>>
>> wonder if I didn't make an implementation mistake ^^
>>
>> Regards,
>> Nikita
>>
>> As we're moving closer to PHP 8 

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Brent Roose]

Hi Nikita

Yes that would be nice, if it's not too much of a hassle. I'm only able to test 
this in one or two large Laravel projects, so it would still be a limited test.

Kind regards
Brent

> On 15 Jul 2020, at 10:53, Nikita Popov  wrote:
> 
> On Wed, Jul 15, 2020 at 10:49 AM Brent Roose  > wrote:
> Hi Nikita
> 
> Is the ini setting available in current 7.4 builds? Is it documented 
> somewhere? I'd like to test this change in some of our projects.
> 
> We did not introduce an ini setting in PHP 7.4, I only used it for my own 
> experiments. The implementation is available at 
> https://github.com/php/php-src/pull/3917 
> . I could rebase that to current 
> 7.4 if that would be useful.
> 
> Nikita
>> On 15 Jul 2020, at 10:28, Nikita Popov > > wrote:
>> 
>> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson > >
>> wrote:
>> 
>>> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
 On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov >>> >
>>> wrote:
 
> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov  >
>>> wrote:
> 
>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski > > wrote:
>> 
>>> 
>>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov >> >
>>> wrote:
>>> 
 Hi internals,
 
 I think it is well known that == in PHP is a pretty big footgun. It
 doesn't
 have to be. I think that type juggling comparisons in a language like
 PHP
 have some merit, it's just that the particular semantics of == in PHP
 make
 it so dangerous. The biggest WTF factor is probably that 0 ==
>>> "foobar"
 returns true.
 
 I'd like to bring forward an RFC for PHP 8 to change the semantics
>>> of ==
 and other non-strict comparisons, when used between a number and a
 string:
 
 https://wiki.php.net/rfc/string_to_number_comparison 
 
 
 The tl;dr is that if you compare a number and a numeric string,
>>> they'll
 be
 compared as numbers. Otherwise, the number is converted into a string
 and
 they'll be compared as strings.
 
 This is a very significant change -- not so much because the actual
>>> BC
 breakage is expected to be particularly large, but because it is a
 silent
 change in core language semantics, which makes it hard to determine
 whether
 or not code is affected by the change. There are things we can do
>>> about
 this, for example the RFC suggests that we might want to have a
 transition
 mode where we perform the comparison using both the old and the new
 semantics and warn if the result differs.
 
 I think we should give serious consideration to making such a change.
 I'd
 be interested to hear whether other people think this is worthwhile,
>>> and
 how we could go about doing it, while minimizing breakage.
 
>>> I generally like the direction and think we should seriously consider
>>> it.
>>> 
>>> I think that before we make any decisions on this, or even dive too
>>> deep
>>> into the discussion - we actually need to implement this behavior,
>>> including the proposed INI setting you mentioned we might add in 7.4
>>> - and
>>> see what happens in some real world apps, at least in terms of
>>> potential
>>> danger (as you say, figuring out whether there's actual breakage would
>>> require a full audit of every potentially problematic sample.
>>> Ultimately,
>>> I think there's no question that if we were to start from scratch,
>>> we'd be
>>> going for something along these lines.  But since we're not starting
>>> from
>>> scratch - scoping the level of breakage is key here.
>>> 
>>> Zeev
>>> 
>> Totally agree that assessing the amount of breakage in real code is key
>> here. I have now implemented a warning for PHP 7.4 (for now
>>> unconditional,
>> no ini setting) that is thrown whenever the result of a comparison is
>>> going
>> to change under the currently proposed rules:
>> https://github.com/php/php-src/pull/3917 
>> 
>> 
>> I've done a few initial tests by running this against the Laravel,
>> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
>>> times
>> for Symfony and 2 times for pear-core. (See PR for the results.)
>> 
>> Both of the warnings in pear-core pointed to implementation bugs. The
>> Symfony warning was due to trailing whitespace not being allowed in
>>> numeric
>> strings (something we should definitel

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Wed, Jul 15, 2020 at 10:49 AM Brent Roose  wrote:

> Hi Nikita
>
> Is the ini setting available in current 7.4 builds? Is it documented
> somewhere? I'd like to test this change in some of our projects.
>

We did not introduce an ini setting in PHP 7.4, I only used it for my own
experiments. The implementation is available at
https://github.com/php/php-src/pull/3917. I could rebase that to current
7.4 if that would be useful.

Nikita

> On 15 Jul 2020, at 10:28, Nikita Popov  wrote:
>
> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson 
> wrote:
>
> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
>
> On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov 
>
> wrote:
>
>
> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov 
>
> wrote:
>
>
> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>
>
> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
> wrote:
>
> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It
> doesn't
> have to be. I think that type juggling comparisons in a language like
> PHP
> have some merit, it's just that the particular semantics of == in PHP
> make
> it so dangerous. The biggest WTF factor is probably that 0 ==
>
> "foobar"
>
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics
>
> of ==
>
> and other non-strict comparisons, when used between a number and a
> string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> The tl;dr is that if you compare a number and a numeric string,
>
> they'll
>
> be
> compared as numbers. Otherwise, the number is converted into a string
> and
> they'll be compared as strings.
>
> This is a very significant change -- not so much because the actual
>
> BC
>
> breakage is expected to be particularly large, but because it is a
> silent
> change in core language semantics, which makes it hard to determine
> whether
> or not code is affected by the change. There are things we can do
>
> about
>
> this, for example the RFC suggests that we might want to have a
> transition
> mode where we perform the comparison using both the old and the new
> semantics and warn if the result differs.
>
> I think we should give serious consideration to making such a change.
> I'd
> be interested to hear whether other people think this is worthwhile,
>
> and
>
> how we could go about doing it, while minimizing breakage.
>
> I generally like the direction and think we should seriously consider
>
> it.
>
>
> I think that before we make any decisions on this, or even dive too
>
> deep
>
> into the discussion - we actually need to implement this behavior,
> including the proposed INI setting you mentioned we might add in 7.4
>
> - and
>
> see what happens in some real world apps, at least in terms of
>
> potential
>
> danger (as you say, figuring out whether there's actual breakage would
> require a full audit of every potentially problematic sample.
>
> Ultimately,
>
> I think there's no question that if we were to start from scratch,
>
> we'd be
>
> going for something along these lines.  But since we're not starting
>
> from
>
> scratch - scoping the level of breakage is key here.
>
> Zeev
>
> Totally agree that assessing the amount of breakage in real code is key
> here. I have now implemented a warning for PHP 7.4 (for now
>
> unconditional,
>
> no ini setting) that is thrown whenever the result of a comparison is
>
> going
>
> to change under the currently proposed rules:
> https://github.com/php/php-src/pull/3917
>
> I've done a few initial tests by running this against the Laravel,
> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
>
> times
>
> for Symfony and 2 times for pear-core. (See PR for the results.)
>
> Both of the warnings in pear-core pointed to implementation bugs. The
> Symfony warning was due to trailing whitespace not being allowed in
>
> numeric
>
> strings (something we should definitely change). One of the Laravel
> warnings is ultimately a false-positive (does not change behavior),
>
> though
>
> code could be improved to avoid it. I wasn't able to tell whether the
>
> other
>
> one is problematic, as it affects sorting order.
>
> I have to say that this is a lot less warnings than I expected. Makes
>
> me
>
> wonder if I didn't make an implementation mistake ^^
>
> Regards,
> Nikita
>
> As we're moving closer to PHP 8 feature freeze, I want to give this RFC
>
> a
>
> bump. I've updated the text to account for some changes that have
>
> happened
>
> in the meantime, such as the removal of locale-sensitivity for float to
> string conversions.
>
> It's been quite a while since we discussed this last, and back then the
> discussion was fairly positive. Some experiments with a warning mode
>
> also
>
> showed that the impact, at least in framework/library code, appears to
>
> be
>
> fairly low in practice, contrary to what one might intuitively expect.
>
> Now would be the time to decide whether or not we want to pursue this
> change for PHP 8.
>
> And then there was silence...

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Brent Roose]

Hi Nikita

Is the ini setting available in current 7.4 builds? Is it documented somewhere? 
I'd like to test this change in some of our projects.

Kind regards
Brent

> On 15 Jul 2020, at 10:28, Nikita Popov  wrote:
> 
> On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson  >
> wrote:
> 
>> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
>>> On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov 
>> wrote:
>>> 
 On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov 
>> wrote:
 
> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
> 
>> 
>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>> wrote:
>> 
>>> Hi internals,
>>> 
>>> I think it is well known that == in PHP is a pretty big footgun. It
>>> doesn't
>>> have to be. I think that type juggling comparisons in a language like
>>> PHP
>>> have some merit, it's just that the particular semantics of == in PHP
>>> make
>>> it so dangerous. The biggest WTF factor is probably that 0 ==
>> "foobar"
>>> returns true.
>>> 
>>> I'd like to bring forward an RFC for PHP 8 to change the semantics
>> of ==
>>> and other non-strict comparisons, when used between a number and a
>>> string:
>>> 
>>> https://wiki.php.net/rfc/string_to_number_comparison
>>> 
>>> The tl;dr is that if you compare a number and a numeric string,
>> they'll
>>> be
>>> compared as numbers. Otherwise, the number is converted into a string
>>> and
>>> they'll be compared as strings.
>>> 
>>> This is a very significant change -- not so much because the actual
>> BC
>>> breakage is expected to be particularly large, but because it is a
>>> silent
>>> change in core language semantics, which makes it hard to determine
>>> whether
>>> or not code is affected by the change. There are things we can do
>> about
>>> this, for example the RFC suggests that we might want to have a
>>> transition
>>> mode where we perform the comparison using both the old and the new
>>> semantics and warn if the result differs.
>>> 
>>> I think we should give serious consideration to making such a change.
>>> I'd
>>> be interested to hear whether other people think this is worthwhile,
>> and
>>> how we could go about doing it, while minimizing breakage.
>>> 
>> I generally like the direction and think we should seriously consider
>> it.
>> 
>> I think that before we make any decisions on this, or even dive too
>> deep
>> into the discussion - we actually need to implement this behavior,
>> including the proposed INI setting you mentioned we might add in 7.4
>> - and
>> see what happens in some real world apps, at least in terms of
>> potential
>> danger (as you say, figuring out whether there's actual breakage would
>> require a full audit of every potentially problematic sample.
>> Ultimately,
>> I think there's no question that if we were to start from scratch,
>> we'd be
>> going for something along these lines.  But since we're not starting
>> from
>> scratch - scoping the level of breakage is key here.
>> 
>> Zeev
>> 
> Totally agree that assessing the amount of breakage in real code is key
> here. I have now implemented a warning for PHP 7.4 (for now
>> unconditional,
> no ini setting) that is thrown whenever the result of a comparison is
>> going
> to change under the currently proposed rules:
> https://github.com/php/php-src/pull/3917
> 
> I've done a few initial tests by running this against the Laravel,
> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
>> times
> for Symfony and 2 times for pear-core. (See PR for the results.)
> 
> Both of the warnings in pear-core pointed to implementation bugs. The
> Symfony warning was due to trailing whitespace not being allowed in
>> numeric
> strings (something we should definitely change). One of the Laravel
> warnings is ultimately a false-positive (does not change behavior),
>> though
> code could be improved to avoid it. I wasn't able to tell whether the
>> other
> one is problematic, as it affects sorting order.
> 
> I have to say that this is a lot less warnings than I expected. Makes
>> me
> wonder if I didn't make an implementation mistake ^^
> 
> Regards,
> Nikita
> 
 As we're moving closer to PHP 8 feature freeze, I want to give this RFC
>> a
 bump. I've updated the text to account for some changes that have
>> happened
 in the meantime, such as the removal of locale-sensitivity for float to
 string conversions.
 
 It's been quite a while since we discussed this last, and back then the
 discussion was fairly positive. Some experiments with a warning mode
>> also
 showed that the impact, at least in framework/library code, appears to
>> be
 fairly low in practice, contrary 

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Tue, Jul 14, 2020 at 11:47 PM Björn Larsson 
wrote:

> Den 2020-07-14 kl. 15:48, skrev Nikita Popov:
> > On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov 
> wrote:
> >
> >> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov 
> wrote:
> >>
> >>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
> >>>
> 
>  On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>  wrote:
> 
> > Hi internals,
> >
> > I think it is well known that == in PHP is a pretty big footgun. It
> > doesn't
> > have to be. I think that type juggling comparisons in a language like
> > PHP
> > have some merit, it's just that the particular semantics of == in PHP
> > make
> > it so dangerous. The biggest WTF factor is probably that 0 ==
> "foobar"
> > returns true.
> >
> > I'd like to bring forward an RFC for PHP 8 to change the semantics
> of ==
> > and other non-strict comparisons, when used between a number and a
> > string:
> >
> > https://wiki.php.net/rfc/string_to_number_comparison
> >
> > The tl;dr is that if you compare a number and a numeric string,
> they'll
> > be
> > compared as numbers. Otherwise, the number is converted into a string
> > and
> > they'll be compared as strings.
> >
> > This is a very significant change -- not so much because the actual
> BC
> > breakage is expected to be particularly large, but because it is a
> > silent
> > change in core language semantics, which makes it hard to determine
> > whether
> > or not code is affected by the change. There are things we can do
> about
> > this, for example the RFC suggests that we might want to have a
> > transition
> > mode where we perform the comparison using both the old and the new
> > semantics and warn if the result differs.
> >
> > I think we should give serious consideration to making such a change.
> > I'd
> > be interested to hear whether other people think this is worthwhile,
> and
> > how we could go about doing it, while minimizing breakage.
> >
>  I generally like the direction and think we should seriously consider
> it.
> 
>  I think that before we make any decisions on this, or even dive too
> deep
>  into the discussion - we actually need to implement this behavior,
>  including the proposed INI setting you mentioned we might add in 7.4
> - and
>  see what happens in some real world apps, at least in terms of
> potential
>  danger (as you say, figuring out whether there's actual breakage would
>  require a full audit of every potentially problematic sample.
> Ultimately,
>  I think there's no question that if we were to start from scratch,
> we'd be
>  going for something along these lines.  But since we're not starting
> from
>  scratch - scoping the level of breakage is key here.
> 
>  Zeev
> 
> >>> Totally agree that assessing the amount of breakage in real code is key
> >>> here. I have now implemented a warning for PHP 7.4 (for now
> unconditional,
> >>> no ini setting) that is thrown whenever the result of a comparison is
> going
> >>> to change under the currently proposed rules:
> >>> https://github.com/php/php-src/pull/3917
> >>>
> >>> I've done a few initial tests by running this against the Laravel,
> >>> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1
> times
> >>> for Symfony and 2 times for pear-core. (See PR for the results.)
> >>>
> >>> Both of the warnings in pear-core pointed to implementation bugs. The
> >>> Symfony warning was due to trailing whitespace not being allowed in
> numeric
> >>> strings (something we should definitely change). One of the Laravel
> >>> warnings is ultimately a false-positive (does not change behavior),
> though
> >>> code could be improved to avoid it. I wasn't able to tell whether the
> other
> >>> one is problematic, as it affects sorting order.
> >>>
> >>> I have to say that this is a lot less warnings than I expected. Makes
> me
> >>> wonder if I didn't make an implementation mistake ^^
> >>>
> >>> Regards,
> >>> Nikita
> >>>
> >> As we're moving closer to PHP 8 feature freeze, I want to give this RFC
> a
> >> bump. I've updated the text to account for some changes that have
> happened
> >> in the meantime, such as the removal of locale-sensitivity for float to
> >> string conversions.
> >>
> >> It's been quite a while since we discussed this last, and back then the
> >> discussion was fairly positive. Some experiments with a warning mode
> also
> >> showed that the impact, at least in framework/library code, appears to
> be
> >> fairly low in practice, contrary to what one might intuitively expect.
> >>
> >> Now would be the time to decide whether or not we want to pursue this
> >> change for PHP 8.
> >>
> > And then there was silence...
> >
> > I think I'll just put this up for vote on Friday, and we'll see what
> people
> > think :)
> >
> > Nikita
>
> Seems like 

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Björn Larsson]

Den 2020-07-14 kl. 15:48, skrev Nikita Popov:

On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov  wrote:


On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov  wrote:


On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:



On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
wrote:


Hi internals,

I think it is well known that == in PHP is a pretty big footgun. It
doesn't
have to be. I think that type juggling comparisons in a language like
PHP
have some merit, it's just that the particular semantics of == in PHP
make
it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
returns true.

I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
and other non-strict comparisons, when used between a number and a
string:

https://wiki.php.net/rfc/string_to_number_comparison

The tl;dr is that if you compare a number and a numeric string, they'll
be
compared as numbers. Otherwise, the number is converted into a string
and
they'll be compared as strings.

This is a very significant change -- not so much because the actual BC
breakage is expected to be particularly large, but because it is a
silent
change in core language semantics, which makes it hard to determine
whether
or not code is affected by the change. There are things we can do about
this, for example the RFC suggests that we might want to have a
transition
mode where we perform the comparison using both the old and the new
semantics and warn if the result differs.

I think we should give serious consideration to making such a change.
I'd
be interested to hear whether other people think this is worthwhile, and
how we could go about doing it, while minimizing breakage.


I generally like the direction and think we should seriously consider it.

I think that before we make any decisions on this, or even dive too deep
into the discussion - we actually need to implement this behavior,
including the proposed INI setting you mentioned we might add in 7.4 - and
see what happens in some real world apps, at least in terms of potential
danger (as you say, figuring out whether there's actual breakage would
require a full audit of every potentially problematic sample.  Ultimately,
I think there's no question that if we were to start from scratch, we'd be
going for something along these lines.  But since we're not starting from
scratch - scoping the level of breakage is key here.

Zeev


Totally agree that assessing the amount of breakage in real code is key
here. I have now implemented a warning for PHP 7.4 (for now unconditional,
no ini setting) that is thrown whenever the result of a comparison is going
to change under the currently proposed rules:
https://github.com/php/php-src/pull/3917

I've done a few initial tests by running this against the Laravel,
Symfony and pear-core. The warning was thrown 2 times for Laravel, 1 times
for Symfony and 2 times for pear-core. (See PR for the results.)

Both of the warnings in pear-core pointed to implementation bugs. The
Symfony warning was due to trailing whitespace not being allowed in numeric
strings (something we should definitely change). One of the Laravel
warnings is ultimately a false-positive (does not change behavior), though
code could be improved to avoid it. I wasn't able to tell whether the other
one is problematic, as it affects sorting order.

I have to say that this is a lot less warnings than I expected. Makes me
wonder if I didn't make an implementation mistake ^^

Regards,
Nikita


As we're moving closer to PHP 8 feature freeze, I want to give this RFC a
bump. I've updated the text to account for some changes that have happened
in the meantime, such as the removal of locale-sensitivity for float to
string conversions.

It's been quite a while since we discussed this last, and back then the
discussion was fairly positive. Some experiments with a warning mode also
showed that the impact, at least in framework/library code, appears to be
fairly low in practice, contrary to what one might intuitively expect.

Now would be the time to decide whether or not we want to pursue this
change for PHP 8.


And then there was silence...

I think I'll just put this up for vote on Friday, and we'll see what people
think :)

Nikita


Seems like a very good idea!! Especially in conjunction with the RFC:
- https://wiki.php.net/rfc/saner-numeric-strings

Btw, in the RFC there is a reference to the "Trailing whitespace in numeric
strings" RFC. Update to reference "Saner numeric strings" RFC instead?

r//Björn L

--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: https://www.php.net/unsub.php

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov  wrote:

> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov  wrote:
>
>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>>
>>>
>>>
>>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>>> wrote:
>>>
 Hi internals,

 I think it is well known that == in PHP is a pretty big footgun. It
 doesn't
 have to be. I think that type juggling comparisons in a language like
 PHP
 have some merit, it's just that the particular semantics of == in PHP
 make
 it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
 returns true.

 I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
 and other non-strict comparisons, when used between a number and a
 string:

 https://wiki.php.net/rfc/string_to_number_comparison

 The tl;dr is that if you compare a number and a numeric string, they'll
 be
 compared as numbers. Otherwise, the number is converted into a string
 and
 they'll be compared as strings.

 This is a very significant change -- not so much because the actual BC
 breakage is expected to be particularly large, but because it is a
 silent
 change in core language semantics, which makes it hard to determine
 whether
 or not code is affected by the change. There are things we can do about
 this, for example the RFC suggests that we might want to have a
 transition
 mode where we perform the comparison using both the old and the new
 semantics and warn if the result differs.

 I think we should give serious consideration to making such a change.
 I'd
 be interested to hear whether other people think this is worthwhile, and
 how we could go about doing it, while minimizing breakage.

>>>
>>> I generally like the direction and think we should seriously consider it.
>>>
>>> I think that before we make any decisions on this, or even dive too deep
>>> into the discussion - we actually need to implement this behavior,
>>> including the proposed INI setting you mentioned we might add in 7.4 - and
>>> see what happens in some real world apps, at least in terms of potential
>>> danger (as you say, figuring out whether there's actual breakage would
>>> require a full audit of every potentially problematic sample.  Ultimately,
>>> I think there's no question that if we were to start from scratch, we'd be
>>> going for something along these lines.  But since we're not starting from
>>> scratch - scoping the level of breakage is key here.
>>>
>>> Zeev
>>>
>>
>> Totally agree that assessing the amount of breakage in real code is key
>> here. I have now implemented a warning for PHP 7.4 (for now unconditional,
>> no ini setting) that is thrown whenever the result of a comparison is going
>> to change under the currently proposed rules:
>> https://github.com/php/php-src/pull/3917
>>
>> I've done a few initial tests by running this against the Laravel,
>> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1 times
>> for Symfony and 2 times for pear-core. (See PR for the results.)
>>
>> Both of the warnings in pear-core pointed to implementation bugs. The
>> Symfony warning was due to trailing whitespace not being allowed in numeric
>> strings (something we should definitely change). One of the Laravel
>> warnings is ultimately a false-positive (does not change behavior), though
>> code could be improved to avoid it. I wasn't able to tell whether the other
>> one is problematic, as it affects sorting order.
>>
>> I have to say that this is a lot less warnings than I expected. Makes me
>> wonder if I didn't make an implementation mistake ^^
>>
>> Regards,
>> Nikita
>>
>
> As we're moving closer to PHP 8 feature freeze, I want to give this RFC a
> bump. I've updated the text to account for some changes that have happened
> in the meantime, such as the removal of locale-sensitivity for float to
> string conversions.
>
> It's been quite a while since we discussed this last, and back then the
> discussion was fairly positive. Some experiments with a warning mode also
> showed that the impact, at least in framework/library code, appears to be
> fairly low in practice, contrary to what one might intuitively expect.
>
> Now would be the time to decide whether or not we want to pursue this
> change for PHP 8.
>

And then there was silence...

I think I'll just put this up for vote on Friday, and we'll see what people
think :)

Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Thu, Jul 2, 2020 at 10:09 AM Nikita Popov  wrote:

> On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov  wrote:
>
>> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>>
>>>
>>>
>>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>>> wrote:
>>>
 Hi internals,

 I think it is well known that == in PHP is a pretty big footgun. It
 doesn't
 have to be. I think that type juggling comparisons in a language like
 PHP
 have some merit, it's just that the particular semantics of == in PHP
 make
 it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
 returns true.

 I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
 and other non-strict comparisons, when used between a number and a
 string:

 https://wiki.php.net/rfc/string_to_number_comparison

 The tl;dr is that if you compare a number and a numeric string, they'll
 be
 compared as numbers. Otherwise, the number is converted into a string
 and
 they'll be compared as strings.

 This is a very significant change -- not so much because the actual BC
 breakage is expected to be particularly large, but because it is a
 silent
 change in core language semantics, which makes it hard to determine
 whether
 or not code is affected by the change. There are things we can do about
 this, for example the RFC suggests that we might want to have a
 transition
 mode where we perform the comparison using both the old and the new
 semantics and warn if the result differs.

 I think we should give serious consideration to making such a change.
 I'd
 be interested to hear whether other people think this is worthwhile, and
 how we could go about doing it, while minimizing breakage.

>>>
>>> I generally like the direction and think we should seriously consider it.
>>>
>>> I think that before we make any decisions on this, or even dive too deep
>>> into the discussion - we actually need to implement this behavior,
>>> including the proposed INI setting you mentioned we might add in 7.4 - and
>>> see what happens in some real world apps, at least in terms of potential
>>> danger (as you say, figuring out whether there's actual breakage would
>>> require a full audit of every potentially problematic sample.  Ultimately,
>>> I think there's no question that if we were to start from scratch, we'd be
>>> going for something along these lines.  But since we're not starting from
>>> scratch - scoping the level of breakage is key here.
>>>
>>> Zeev
>>>
>>
>> Totally agree that assessing the amount of breakage in real code is key
>> here. I have now implemented a warning for PHP 7.4 (for now unconditional,
>> no ini setting) that is thrown whenever the result of a comparison is going
>> to change under the currently proposed rules:
>> https://github.com/php/php-src/pull/3917
>>
>> I've done a few initial tests by running this against the Laravel,
>> Symfony and pear-core. The warning was thrown 2 times for Laravel, 1 times
>> for Symfony and 2 times for pear-core. (See PR for the results.)
>>
>> Both of the warnings in pear-core pointed to implementation bugs. The
>> Symfony warning was due to trailing whitespace not being allowed in numeric
>> strings (something we should definitely change). One of the Laravel
>> warnings is ultimately a false-positive (does not change behavior), though
>> code could be improved to avoid it. I wasn't able to tell whether the other
>> one is problematic, as it affects sorting order.
>>
>> I have to say that this is a lot less warnings than I expected. Makes me
>> wonder if I didn't make an implementation mistake ^^
>>
>> Regards,
>> Nikita
>>
>
> As we're moving closer to PHP 8 feature freeze, I want to give this RFC a
> bump. I've updated the text to account for some changes that have happened
> in the meantime, such as the removal of locale-sensitivity for float to
> string conversions.
>
> It's been quite a while since we discussed this last, and back then the
> discussion was fairly positive. Some experiments with a warning mode also
> showed that the impact, at least in framework/library code, appears to be
> fairly low in practice, contrary to what one might intuitively expect.
>
> Now would be the time to decide whether or not we want to pursue this
> change for PHP 8.
>

Thinking about the detailed behavior of the RFC, I think it might be better
to change the semantics to:

> If one of the operands is NaN, return uncomparable (1).
> Otherwise, convert the int/float operand to string with precision=-1 and
compare both operands as strings (with the usual "smart" logic).

This differs from what the RFC currently specifies only in the behavior of
comparison between a float and a non-numeric strings (because the string
representation of the float currently depends on precision), but I think
specifying it this way simplifies the mental model behind it, and makes the
i

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Mon, Mar 4, 2019 at 6:00 PM Nikita Popov  wrote:

> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>
>>
>>
>> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov 
>> wrote:
>>
>>> Hi internals,
>>>
>>> I think it is well known that == in PHP is a pretty big footgun. It
>>> doesn't
>>> have to be. I think that type juggling comparisons in a language like PHP
>>> have some merit, it's just that the particular semantics of == in PHP
>>> make
>>> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
>>> returns true.
>>>
>>> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
>>> and other non-strict comparisons, when used between a number and a
>>> string:
>>>
>>> https://wiki.php.net/rfc/string_to_number_comparison
>>>
>>> The tl;dr is that if you compare a number and a numeric string, they'll
>>> be
>>> compared as numbers. Otherwise, the number is converted into a string and
>>> they'll be compared as strings.
>>>
>>> This is a very significant change -- not so much because the actual BC
>>> breakage is expected to be particularly large, but because it is a silent
>>> change in core language semantics, which makes it hard to determine
>>> whether
>>> or not code is affected by the change. There are things we can do about
>>> this, for example the RFC suggests that we might want to have a
>>> transition
>>> mode where we perform the comparison using both the old and the new
>>> semantics and warn if the result differs.
>>>
>>> I think we should give serious consideration to making such a change. I'd
>>> be interested to hear whether other people think this is worthwhile, and
>>> how we could go about doing it, while minimizing breakage.
>>>
>>
>> I generally like the direction and think we should seriously consider it.
>>
>> I think that before we make any decisions on this, or even dive too deep
>> into the discussion - we actually need to implement this behavior,
>> including the proposed INI setting you mentioned we might add in 7.4 - and
>> see what happens in some real world apps, at least in terms of potential
>> danger (as you say, figuring out whether there's actual breakage would
>> require a full audit of every potentially problematic sample.  Ultimately,
>> I think there's no question that if we were to start from scratch, we'd be
>> going for something along these lines.  But since we're not starting from
>> scratch - scoping the level of breakage is key here.
>>
>> Zeev
>>
>
> Totally agree that assessing the amount of breakage in real code is key
> here. I have now implemented a warning for PHP 7.4 (for now unconditional,
> no ini setting) that is thrown whenever the result of a comparison is going
> to change under the currently proposed rules:
> https://github.com/php/php-src/pull/3917
>
> I've done a few initial tests by running this against the Laravel, Symfony
> and pear-core. The warning was thrown 2 times for Laravel, 1 times for
> Symfony and 2 times for pear-core. (See PR for the results.)
>
> Both of the warnings in pear-core pointed to implementation bugs. The
> Symfony warning was due to trailing whitespace not being allowed in numeric
> strings (something we should definitely change). One of the Laravel
> warnings is ultimately a false-positive (does not change behavior), though
> code could be improved to avoid it. I wasn't able to tell whether the other
> one is problematic, as it affects sorting order.
>
> I have to say that this is a lot less warnings than I expected. Makes me
> wonder if I didn't make an implementation mistake ^^
>
> Regards,
> Nikita
>

As we're moving closer to PHP 8 feature freeze, I want to give this RFC a
bump. I've updated the text to account for some changes that have happened
in the meantime, such as the removal of locale-sensitivity for float to
string conversions.

It's been quite a while since we discussed this last, and back then the
discussion was fairly positive. Some experiments with a warning mode also
showed that the impact, at least in framework/library code, appears to be
fairly low in practice, contrary to what one might intuitively expect.

Now would be the time to decide whether or not we want to pursue this
change for PHP 8.

Regards,
Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Niklas Keller]

Am Mo., 4. März 2019 um 18:00 Uhr schrieb Nikita Popov :
>
> On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:
>
> >
> >
> > On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov  wrote:
> >
> >> Hi internals,
> >>
> >> I think it is well known that == in PHP is a pretty big footgun. It
> >> doesn't
> >> have to be. I think that type juggling comparisons in a language like PHP
> >> have some merit, it's just that the particular semantics of == in PHP make
> >> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> >> returns true.
> >>
> >> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> >> and other non-strict comparisons, when used between a number and a string:
> >>
> >> https://wiki.php.net/rfc/string_to_number_comparison
> >>
> >> The tl;dr is that if you compare a number and a numeric string, they'll be
> >> compared as numbers. Otherwise, the number is converted into a string and
> >> they'll be compared as strings.
> >>
> >> This is a very significant change -- not so much because the actual BC
> >> breakage is expected to be particularly large, but because it is a silent
> >> change in core language semantics, which makes it hard to determine
> >> whether
> >> or not code is affected by the change. There are things we can do about
> >> this, for example the RFC suggests that we might want to have a transition
> >> mode where we perform the comparison using both the old and the new
> >> semantics and warn if the result differs.
> >>
> >> I think we should give serious consideration to making such a change. I'd
> >> be interested to hear whether other people think this is worthwhile, and
> >> how we could go about doing it, while minimizing breakage.
> >>
> >
> > I generally like the direction and think we should seriously consider it.
> >
> > I think that before we make any decisions on this, or even dive too deep
> > into the discussion - we actually need to implement this behavior,
> > including the proposed INI setting you mentioned we might add in 7.4 - and
> > see what happens in some real world apps, at least in terms of potential
> > danger (as you say, figuring out whether there's actual breakage would
> > require a full audit of every potentially problematic sample.  Ultimately,
> > I think there's no question that if we were to start from scratch, we'd be
> > going for something along these lines.  But since we're not starting from
> > scratch - scoping the level of breakage is key here.
> >
> > Zeev
> >
>
> Totally agree that assessing the amount of breakage in real code is key
> here. I have now implemented a warning for PHP 7.4 (for now unconditional,
> no ini setting) that is thrown whenever the result of a comparison is going
> to change under the currently proposed rules:
> https://github.com/php/php-src/pull/3917
>
> I've done a few initial tests by running this against the Laravel, Symfony
> and pear-core. The warning was thrown 2 times for Laravel, 1 times for
> Symfony and 2 times for pear-core. (See PR for the results.)
>
> Both of the warnings in pear-core pointed to implementation bugs. The
> Symfony warning was due to trailing whitespace not being allowed in numeric
> strings (something we should definitely change). One of the Laravel
> warnings is ultimately a false-positive (does not change behavior), though
> code could be improved to avoid it. I wasn't able to tell whether the other
> one is problematic, as it affects sorting order.
>
> I have to say that this is a lot less warnings than I expected. Makes me
> wonder if I didn't make an implementation mistake ^^
>
> Regards,
> Nikita

Most warnings will not come from framework code, but code interfacing
with browsers, I guess.

Regards, Niklas

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Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Wed, Feb 27, 2019 at 10:23 AM Zeev Suraski  wrote:

>
>
> On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov  wrote:
>
>> Hi internals,
>>
>> I think it is well known that == in PHP is a pretty big footgun. It
>> doesn't
>> have to be. I think that type juggling comparisons in a language like PHP
>> have some merit, it's just that the particular semantics of == in PHP make
>> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
>> returns true.
>>
>> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
>> and other non-strict comparisons, when used between a number and a string:
>>
>> https://wiki.php.net/rfc/string_to_number_comparison
>>
>> The tl;dr is that if you compare a number and a numeric string, they'll be
>> compared as numbers. Otherwise, the number is converted into a string and
>> they'll be compared as strings.
>>
>> This is a very significant change -- not so much because the actual BC
>> breakage is expected to be particularly large, but because it is a silent
>> change in core language semantics, which makes it hard to determine
>> whether
>> or not code is affected by the change. There are things we can do about
>> this, for example the RFC suggests that we might want to have a transition
>> mode where we perform the comparison using both the old and the new
>> semantics and warn if the result differs.
>>
>> I think we should give serious consideration to making such a change. I'd
>> be interested to hear whether other people think this is worthwhile, and
>> how we could go about doing it, while minimizing breakage.
>>
>
> I generally like the direction and think we should seriously consider it.
>
> I think that before we make any decisions on this, or even dive too deep
> into the discussion - we actually need to implement this behavior,
> including the proposed INI setting you mentioned we might add in 7.4 - and
> see what happens in some real world apps, at least in terms of potential
> danger (as you say, figuring out whether there's actual breakage would
> require a full audit of every potentially problematic sample.  Ultimately,
> I think there's no question that if we were to start from scratch, we'd be
> going for something along these lines.  But since we're not starting from
> scratch - scoping the level of breakage is key here.
>
> Zeev
>

Totally agree that assessing the amount of breakage in real code is key
here. I have now implemented a warning for PHP 7.4 (for now unconditional,
no ini setting) that is thrown whenever the result of a comparison is going
to change under the currently proposed rules:
https://github.com/php/php-src/pull/3917

I've done a few initial tests by running this against the Laravel, Symfony
and pear-core. The warning was thrown 2 times for Laravel, 1 times for
Symfony and 2 times for pear-core. (See PR for the results.)

Both of the warnings in pear-core pointed to implementation bugs. The
Symfony warning was due to trailing whitespace not being allowed in numeric
strings (something we should definitely change). One of the Laravel
warnings is ultimately a false-positive (does not change behavior), though
code could be improved to avoid it. I wasn't able to tell whether the other
one is problematic, as it affects sorting order.

I have to say that this is a lot less warnings than I expected. Makes me
wonder if I didn't make an implementation mistake ^^

Regards,
Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Gabriel Caruso]

Em ter, 26 de fev de 2019 às 09:28, Nikita Popov 
escreveu:

> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It doesn't
> have to be. I think that type juggling comparisons in a language like PHP
> have some merit, it's just that the particular semantics of == in PHP make
> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> and other non-strict comparisons, when used between a number and a string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> The tl;dr is that if you compare a number and a numeric string, they'll be
> compared as numbers. Otherwise, the number is converted into a string and
> they'll be compared as strings.
>
> This is a very significant change -- not so much because the actual BC
> breakage is expected to be particularly large, but because it is a silent
> change in core language semantics, which makes it hard to determine whether
> or not code is affected by the change. There are things we can do about
> this, for example the RFC suggests that we might want to have a transition
> mode where we perform the comparison using both the old and the new
> semantics and warn if the result differs.
>
> I think we should give serious consideration to making such a change. I'd
> be interested to hear whether other people think this is worthwhile, and
> how we could go about doing it, while minimizing breakage.
>
> Regards,
> Nikita
>

Hi Nikita,

There's only one case that I'm not sure about

> Comparison| Before | After
> --
>  0 == ""  | true   | false

I know that a cast of am empty and non-empty string results into 0 (
https://3v4l.org/W0P3Z), but still, not sure about this one in specific.

Best,
-- 
Gabriel Caruso

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Zeev Suraski]

On Tue, Feb 26, 2019 at 2:27 PM Nikita Popov  wrote:

> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It doesn't
> have to be. I think that type juggling comparisons in a language like PHP
> have some merit, it's just that the particular semantics of == in PHP make
> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> and other non-strict comparisons, when used between a number and a string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> The tl;dr is that if you compare a number and a numeric string, they'll be
> compared as numbers. Otherwise, the number is converted into a string and
> they'll be compared as strings.
>
> This is a very significant change -- not so much because the actual BC
> breakage is expected to be particularly large, but because it is a silent
> change in core language semantics, which makes it hard to determine whether
> or not code is affected by the change. There are things we can do about
> this, for example the RFC suggests that we might want to have a transition
> mode where we perform the comparison using both the old and the new
> semantics and warn if the result differs.
>
> I think we should give serious consideration to making such a change. I'd
> be interested to hear whether other people think this is worthwhile, and
> how we could go about doing it, while minimizing breakage.
>

I generally like the direction and think we should seriously consider it.

I think that before we make any decisions on this, or even dive too deep
into the discussion - we actually need to implement this behavior,
including the proposed INI setting you mentioned we might add in 7.4 - and
see what happens in some real world apps, at least in terms of potential
danger (as you say, figuring out whether there's actual breakage would
require a full audit of every potentially problematic sample.  Ultimately,
I think there's no question that if we were to start from scratch, we'd be
going for something along these lines.  But since we're not starting from
scratch - scoping the level of breakage is key here.

Zeev

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Claude Pache]

> Le 27 févr. 2019 à 09:06, Kingsquare.nl - Robin Speekenbrink 
>  a écrit :
> 
> As of the 0 == "" bit: I do think that an empty string is widespread
> regarded as falsey-string... Thus 0 == "" sould IMHO return true...
> 

0 == "" evaluating to true has been a footgun for me in the past; something 
like that:

```php
$state = $_GET['state'] ?? null;
// ...
switch ($state) {
case 0: // when $state === "", this branch is incorrectly chosen
// ...
}
```

where the `state` parameter comes from  and is supposed to 
provide an optional filter criterion for some list.

The fact that both values are falsy doesn’t mean that they should be equal 
(hopefully, `array() == 0` evaluates to false).

—Claude

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Arvids Godjuks]

ср, 27 февр. 2019 г. в 10:06, Kingsquare.nl - Robin Speekenbrink <
ro...@kingsquare.nl>:

> Op di 26 feb. 2019 om 13:27 schreef Nikita Popov :
>
> > Hi internals,
> >
> > I think it is well known that == in PHP is a pretty big footgun. It
> doesn't
> > have to be. I think that type juggling comparisons in a language like PHP
> > have some merit, it's just that the particular semantics of == in PHP
> make
> > it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> > returns true.
> >
> > I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> > and other non-strict comparisons, when used between a number and a
> string:
> >
> > https://wiki.php.net/rfc/string_to_number_comparison
> >
> > ...
> >
> > Regards,
> > Nikita
> >
>
> Dear All,
>
> From a user-space POV this is a very good way forward and I (personally)
> really like the proposal of having a transitional period (7.4 anyone?)
>
> As of the 0 == "" bit: I do think that an empty string is widespread
> regarded as falsey-string... Thus 0 == "" sould IMHO return true...
>
> Just my 2 cents, keep up the excellent Nikita!
> (and everyone else ofcourse)
>
> Regards,
> Robin
>

It's a bad idea to leave 0 == "" - remember - we are dealing with strings
that come in via HTTP, so when you handle form input a 0 can be a valid
input value, but an empty string is not.
Sure, a === is better used here or empty(), but we should not leave
edge cases like these. This is a string to a number comparison - it should
trigger notice or error or whatever is designed to happen when "abc" == 123
is being done.
-- 
Arvīds Godjuks

+371 26 851 664
arvids.godj...@gmail.com
Skype: psihius
Telegram: @psihius https://t.me/psihius

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Kingsquare.nl - Robin Speekenbrink]

Op di 26 feb. 2019 om 13:27 schreef Nikita Popov :

> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It doesn't
> have to be. I think that type juggling comparisons in a language like PHP
> have some merit, it's just that the particular semantics of == in PHP make
> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> and other non-strict comparisons, when used between a number and a string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> ...
>
> Regards,
> Nikita
>

Dear All,

>From a user-space POV this is a very good way forward and I (personally)
really like the proposal of having a transitional period (7.4 anyone?)

As of the 0 == "" bit: I do think that an empty string is widespread
regarded as falsey-string... Thus 0 == "" sould IMHO return true...

Just my 2 cents, keep up the excellent Nikita!
(and everyone else ofcourse)

Regards,
Robin

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Dmitry Stogov]

Hi Nikita,


Yeah, this is a big BC break, but I think, it's a good time to make some 
"cleanup" in PHP-8.

The only thing, I don't like is a difference between leading and trailing 
spaces.

They should behave in the same way.


Thanks. Dmitry.


From: Nikita Popov 
Sent: Tuesday, February 26, 2019 3:27:23 PM
To: PHP internals
Subject: [PHP-DEV] [RFC] Saner string to number comparisons

Hi internals,

I think it is well known that == in PHP is a pretty big footgun. It doesn't
have to be. I think that type juggling comparisons in a language like PHP
have some merit, it's just that the particular semantics of == in PHP make
it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
returns true.

I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
and other non-strict comparisons, when used between a number and a string:

https://wiki.php.net/rfc/string_to_number_comparison

The tl;dr is that if you compare a number and a numeric string, they'll be
compared as numbers. Otherwise, the number is converted into a string and
they'll be compared as strings.

This is a very significant change -- not so much because the actual BC
breakage is expected to be particularly large, but because it is a silent
change in core language semantics, which makes it hard to determine whether
or not code is affected by the change. There are things we can do about
this, for example the RFC suggests that we might want to have a transition
mode where we perform the comparison using both the old and the new
semantics and warn if the result differs.

I think we should give serious consideration to making such a change. I'd
be interested to hear whether other people think this is worthwhile, and
how we could go about doing it, while minimizing breakage.

Regards,
Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Rowan Collins]

On 26 February 2019 13:26:24 GMT+00:00, Nikita Popov  
wrote:
>I'm mentioning this, because it is a precedent for tweaking the string
>to
>string numeric comparison rules to prevent unexpected and possibly
>security
>critical equalities. I think we could add similar special handling for
>the
>"0e" == "0e" case, as this is another "catastrophic" case when
>it
>comes to comparisons of hashes that happen to start with 0e, for
>example.

That makes sense. Personally, I find the treatment of strings in this 
e-notation problematic in all contexts - it makes is_numeric() much less useful 
for validation, for instance - but realise we have to balance compatibility 
here.


>It might be better to discuss such a change separately from this
>proposal
>though (it's much more minor, and something that can also conceivable
>go
>into a minor version, given that the previous change was applied in a
>patch
>release).

I think keeping it to a separate RFC is fine, but it would be nice to target 
the same release. "We've made == safer" is something that we can shout about, 
even if it's composed of a bunch of small tweaks. It also gives one upgrade 
where people need to look for subtle breaks, rather than two.

Regards,

-- 
Rowan Collins
[IMSoP]

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Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

On Tue, Feb 26, 2019 at 2:06 PM Rowan Collins 
wrote:

> On Tue, 26 Feb 2019 at 12:27, Nikita Popov  wrote:
>
> > I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> > and other non-strict comparisons, when used between a number and a
> string:
> >
> > https://wiki.php.net/rfc/string_to_number_comparison
> >
>
>
> Hi Nikita,
>
> Thanks for tackling this; I think if we can improve this, we'll be
> answering a lot of language critics (I'm sure they'll find something else
> to complain about, but that's life!).
>
> However, I'm concerned that it doesn't go far enough, when you say that the
> following will still return true:
>
> 0 == "0e214987142012"
> "0" == "0e214987142012"
>
> I think the cases where this is useful are vastly outweighed by the cases
> where it's completely unexpected, and potentially dangerous (e.g. in a hash
> comparison). If this is not fixed, the "dogma to always avoid non-strict
> comparisons" you refer to will remain.
>
> If I understand it right, this arises from the fact that "0e214987142012"
> is considered a "well-formed numeric string", which is cast to int(0) or
> float(0). Is it feasible to also narrow this definition as part of the same
> change?
>

Yes, that's right. However, it's probably worth mentioning that string to
string comparisons are subject to additional constraints beyond the
well-formedness requirement. Since PHP 5.4.4 there are additional overflow
protections in place, which prevent numeric comparison from applying when
both sides are integers that overflow to double and become equal as a
result of that. This means that "1" ==
"10001" returns false rather than true since PHP 5.4.4.

I'm mentioning this, because it is a precedent for tweaking the string to
string numeric comparison rules to prevent unexpected and possibly security
critical equalities. I think we could add similar special handling for the
"0e" == "0e" case, as this is another "catastrophic" case when it
comes to comparisons of hashes that happen to start with 0e, for example.

It might be better to discuss such a change separately from this proposal
though (it's much more minor, and something that can also conceivable go
into a minor version, given that the previous change was applied in a patch
release).

Regards,
Nikita

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[Rowan Collins]

On Tue, 26 Feb 2019 at 12:27, Nikita Popov  wrote:

> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> and other non-strict comparisons, when used between a number and a string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>


Hi Nikita,

Thanks for tackling this; I think if we can improve this, we'll be
answering a lot of language critics (I'm sure they'll find something else
to complain about, but that's life!).

However, I'm concerned that it doesn't go far enough, when you say that the
following will still return true:

0 == "0e214987142012"
"0" == "0e214987142012"

I think the cases where this is useful are vastly outweighed by the cases
where it's completely unexpected, and potentially dangerous (e.g. in a hash
comparison). If this is not fixed, the "dogma to always avoid non-strict
comparisons" you refer to will remain.

If I understand it right, this arises from the fact that "0e214987142012"
is considered a "well-formed numeric string", which is cast to int(0) or
float(0). Is it feasible to also narrow this definition as part of the same
change?

Regards,
-- 
Rowan Collins
[IMSoP]

Re: [PHP-DEV] [RFC] Saner string to number comparisons

[G. P. B.]

On Tue, 26 Feb 2019 at 13:27, Nikita Popov  wrote:

> Hi internals,
>
> I think it is well known that == in PHP is a pretty big footgun. It doesn't
> have to be. I think that type juggling comparisons in a language like PHP
> have some merit, it's just that the particular semantics of == in PHP make
> it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
> returns true.
>
> I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
> and other non-strict comparisons, when used between a number and a string:
>
> https://wiki.php.net/rfc/string_to_number_comparison
>
> The tl;dr is that if you compare a number and a numeric string, they'll be
> compared as numbers. Otherwise, the number is converted into a string and
> they'll be compared as strings.
>
> This is a very significant change -- not so much because the actual BC
> breakage is expected to be particularly large, but because it is a silent
> change in core language semantics, which makes it hard to determine whether
> or not code is affected by the change. There are things we can do about
> this, for example the RFC suggests that we might want to have a transition
> mode where we perform the comparison using both the old and the new
> semantics and warn if the result differs.
>
> I think we should give serious consideration to making such a change. I'd
> be interested to hear whether other people think this is worthwhile, and
> how we could go about doing it, while minimizing breakage.
>
> Regards,
> Nikita
>

I am in favor of this change however I do think having the Trailing
Whitespaces numerics RFC
would be better for this change as I do agree with you that IMHO 42 == "42
" should return true.
I'm also not sure if you maybe should point this out sooner but as it is
currently seems fine to me.

However small nitpick on your precision section

$float = 1.75;
 ini_set ('precision', 14); //
Defaultvar_dump ($float < "1.75abc");//
Behaves likevar_dump ("1.75" <
"1.75abc"); // true

is wrong because var_dump($float < "1.75abc"); returns false:
https://3v4l.org/G56Vj
I think you meant to use the <= comparison operator maybe?

Also the NAN behavior is a bit surprising (to me atleast) but it does
follow the IEEE-754
However I don't really understand why it always returns 1 with the TIE
operator.

And finally as to how to do the transition I don't really have a strong
opinion about it.
An INI setting seems like this behavior is going to be supported for a long
time.
But it doesn't seem like its possible to throw deprecation notices to alert
of this change.

Best regards

George P. Banyard

[PHP-DEV] [RFC] Saner string to number comparisons

[Nikita Popov]

Hi internals,

I think it is well known that == in PHP is a pretty big footgun. It doesn't
have to be. I think that type juggling comparisons in a language like PHP
have some merit, it's just that the particular semantics of == in PHP make
it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
returns true.

I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
and other non-strict comparisons, when used between a number and a string:

https://wiki.php.net/rfc/string_to_number_comparison

The tl;dr is that if you compare a number and a numeric string, they'll be
compared as numbers. Otherwise, the number is converted into a string and
they'll be compared as strings.

This is a very significant change -- not so much because the actual BC
breakage is expected to be particularly large, but because it is a silent
change in core language semantics, which makes it hard to determine whether
or not code is affected by the change. There are things we can do about
this, for example the RFC suggests that we might want to have a transition
mode where we perform the comparison using both the old and the new
semantics and warn if the result differs.

I think we should give serious consideration to making such a change. I'd
be interested to hear whether other people think this is worthwhile, and
how we could go about doing it, while minimizing breakage.

Regards,
Nikita