php-general Digest 2 Jan 2013 12:31:56 -0000 Issue 8083
php-general Digest 2 Jan 2013 12:31:56 - Issue 8083
Topics (messages 319992 through 319992):
Is there any difference in assigning variable to itself after some actions on
it or to another variable?
319992 by: Vyacheslav Kondratyuk
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--
---BeginMessage---
Hi,
Not long ago I had a debates about assignment variables to itself after
some action on them.
Assign variable to itself [AI]:
echo memory_get_usage() . \n; // 645680
$repeatedString = str_repeat('Hello,', 1);
echo memory_get_usage() . \n; // 705944, AI_delta1 = 60264
$repeatedString = explode(',', $repeatedString);
echo memory_get_usage() . \n; // 3337888, AI_delta2 = 2631944
echo memory_get_peak_usage() . \n; // AI_peak = 3401024
Assign variable to another variable [AAV]:
echo memory_get_usage() . \n; // 645752
$repeatedString = str_repeat('Hello,', 1);
echo memory_get_usage() . \n; // 706024, AAV_delta1 = 60272
$explodedString = explode(',', $repeatedString);
echo memory_get_usage() . \n; // 3398256, AAV_delta2 = 2692232
echo memory_get_peak_usage() . \n; // AAV_peak = 3400984
I created tests of memory usage in both cases and subtract values:
AAV_delta1 - AI_delta = 8
AAV_delta2 - AI_delta2 = 60288
AAV_peak - AI_peak = -40
According to this results it doesn't matter which approach to use, memory
usage - same. It's only a question should I use variable $repeatedString at
my code below or not.
Am I right at my conclusions or my tests are not correct?
Why it happens this way?
Also a question: AAV_delta1 - AI_delta = 8, I expect it should be equal 0.
Why it's equals 8?
Note: Memory usage can vary on your system.
PHP Version: 5.3.5-1ubuntu7.11.
---End Message---
php-general Digest 3 Jan 2013 03:17:46 -0000 Issue 8084
php-general Digest 3 Jan 2013 03:17:46 - Issue 8084
Topics (messages 319993 through 320002):
Boolean type forced on string assignment inside if statement
319993 by: Marc Guay
319994 by: Marc Guay
319995 by: Stephen
319996 by: Tim Streater
319997 by: Jim Lucas
319998 by: Marc Guay
31 by: Jim Lucas
32 by: Marc Guay
320001 by: Marc Guay
320002 by: tamouse mailing lists
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--
---BeginMessage---
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
Marc
---End Message---
---BeginMessage---
Interesting that if I wrap them up tighter in braces I get the desires result..
if (($a = foo) ($b = bar)){
echo $a.br /.$b;
}
Returns
foo
bar
---End Message---
---BeginMessage---
On 13-01-02 10:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
takes precedence over =
http://php.net/manual/en/language.operators.precedence.php
You may want to use brackets
--
Stephen
---End Message---
---BeginMessage---
On 02 Jan 2013 at 16:05, Stephen stephe...@rogers.com wrote:
On 13-01-02 10:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
takes precedence over =
http://php.net/manual/en/language.operators.precedence.php
You may want to use brackets
OP may want to avoid doing something unusual which may confuse a casual reader.
--
Cheers -- Tim
---End Message---
---BeginMessage---
On 01/02/2013 07:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
Marc
Why would you do this.
I cannot envision a time or condition that would require such a test.
Can you please explain why you would want to do this?
Won't this type of condition/test always return true?
--
Jim Lucas
http://www.cmsws.com/
http://www.cmsws.com/examples/
---End Message---
---BeginMessage---
Won't this type of condition/test always return true?
I simplified the example. In my real life case the foo and bar
are variables which can be empty strings, and if they both are not, I
would like to display them.
Marc
---End Message---
---BeginMessage---
On 01/02/2013 10:21 AM, Marc Guay wrote:
Won't this type of condition/test always return true?
I simplified the example. In my real life case the foo and bar
are variables which can be empty strings, and if they both are not, I
would like to display them.
Marc
Then why not use empty()?
$a = foo;
$b = bar;
if ( !empty($a) !empty($b) ){
echo $a.br /.$b;
}
The reason I ask is that what if one of your strings was a 0 (zero) I
would expect your code would not work as you had intended.
php -r 'if ( $a=foo $b=0 ) { echo \n\n{$a}\n{$b}\n\n; }'
In my testing, it does not. I would then have to ask, how often do you
think a string will be 0?
--
Jim Lucas
http://www.cmsws.com/
http://www.cmsws.com/examples/
---End Message---
---BeginMessage---
Thanks for the head's up. In this case the string will be an English
sentence when it's populated properly so that won't be a concern.
Marc
---End Message---
---BeginMessage---
Something else that's happening with this, which makes it a Bad Idea
(tm) is that when the operator is or, as it is in my real life
scenerio, the 2nd variable occasionally doesn't get populated if the
first one returns true.
if ($a = foo || $b = bar){
echo $a.br /.$b;
}
Returns
foo
And even worse, because I have this in a loop, what can happen is that
if $b gets populated on one loop, it doesn't get reset for the next
one so the data gets seriously bungled.
Moral of the story: Don't be so fancy on your first day back after
vacation. :)
Marc
---End Message---
---BeginMessage---
On Wed, Jan 2, 2013 at 1:02 PM, Marc Guay marc.g...@gmail.com wrote:
Something else that's happening with this, which makes it a Bad Idea
(tm) is that when the operator is or, as it is in my real life
scenerio, the 2nd variable occasionally doesn't get populated if the
first one returns true.
if ($a = foo || $b = bar){
echo $a.br /.$b;
}
Returns
foo
And even worse, because I have this in a loop, what can happen is that
if $b gets populated on one loop, it doesn't get reset for the next
one so the data gets seriously bungled.
Ah, yeah, seriously, don't mix assignments and tests up this way
unless it doesn't matter that the second part never gets set. It's
called short-circuiting, and nearly every language (the
Re: [PHP] Boolean type forced on string assignment inside if statement
On 13-01-02 10:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
takes precedence over =
http://php.net/manual/en/language.operators.precedence.php
You may want to use brackets
--
Stephen
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[PHP] Re: Boolean type forced on string assignment inside if statement
On 02 Jan 2013 at 16:05, Stephen stephe...@rogers.com wrote:
On 13-01-02 10:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
takes precedence over =
http://php.net/manual/en/language.operators.precedence.php
You may want to use brackets
OP may want to avoid doing something unusual which may confuse a casual reader.
--
Cheers -- Tim
--
PHP General Mailing List (http://www.php.net/)
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Re: [PHP] Boolean type forced on string assignment inside if statement
On 01/02/2013 07:53 AM, Marc Guay wrote:
Hi folks,
if ($a = foo $b = bar){
echo $a.br /.$b;
}
Returns:
1
bar
I expect:
foo
bar
Is this documented?
Marc
Why would you do this.
I cannot envision a time or condition that would require such a test.
Can you please explain why you would want to do this?
Won't this type of condition/test always return true?
--
Jim Lucas
http://www.cmsws.com/
http://www.cmsws.com/examples/
--
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Re: [PHP] Boolean type forced on string assignment inside if statement
On 01/02/2013 10:21 AM, Marc Guay wrote:
Won't this type of condition/test always return true?
I simplified the example. In my real life case the foo and bar
are variables which can be empty strings, and if they both are not, I
would like to display them.
Marc
Then why not use empty()?
$a = foo;
$b = bar;
if ( !empty($a) !empty($b) ){
echo $a.br /.$b;
}
The reason I ask is that what if one of your strings was a 0 (zero) I
would expect your code would not work as you had intended.
php -r 'if ( $a=foo $b=0 ) { echo \n\n{$a}\n{$b}\n\n; }'
In my testing, it does not. I would then have to ask, how often do you
think a string will be 0?
--
Jim Lucas
http://www.cmsws.com/
http://www.cmsws.com/examples/
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