Re: [PHP-DEV] wrong implementation of isset()?
At 03:02 AM 2/7/2001 +0100, Cynic wrote:
with all respect to the people who develop the language, I
think this is nonsense:
$rs = mysql_query( 'select x, y, z from foo where ...' ) ;
$x = mysql_fetch_array( $rs , MYSQL_NUM ) ;
var_dump( $x[2] ) ;
var_dump( isset( $x[2] ) ) ;
NULL # well, the column contains null values
bool(false)
But since (almost) everybody else disagrees, I must be missing
something obvious.
BTW, does $x = null really equal to unset( $x ) or does
isset() just get fooled by its value?
unset() removes it from the symbol table and $x = NULL; changes it to be a
NULL value. As far as PHP scripts are concerned it's pretty much the same
thing. There are certain situations where you can't really nuke the
variable but you want to mark it as dead.
In any case, you can always use the === operator to check if something is
really NULL and not false.
if ($x === NULL) {
}
I can't remember off hand all the reasons for isset(NULL) being false but
the main reason is that it makes a lot of sense because what the NULL value
is supposed to mean is that there's no value. Also it allows us to
differentiate between functions returning bool(false) and null values.
Hence also the === operator.
I really think that if your script differentiates between these two cases
you might not be writing it very well.
OK, I know it's a messy Email. I'm on the way to bed but I hope it
clarifies a few things :)
Andi
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[PHP-DEV] wrong implementation of isset()?
The following was reported today in the german language newsgroup
news:de.comp.lang.php:
?php
$a = NULL;
if (isset($a)) { print "ok, du hast recht"; }
?
Shouldn't this script generate some output? IMO $a is set
and isset() should return true.
The manual says:
"isset -- Determine whether a variable is set"
So following the manual means that there _has_ to be
output because $a is set in fact.
Or am I wrong?
-Martin
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Re: [PHP-DEV] wrong implementation of isset()?
On Tue, 06 Feb 2001, Martin Jansen wrote:
The following was reported today in the german language newsgroup
news:de.comp.lang.php:
?php
$a = NULL;
if (isset($a)) { print "ok, du hast recht"; }
?
Shouldn't this script generate some output? IMO $a is set
and isset() should return true.
The manual says:
"isset -- Determine whether a variable is set"
So following the manual means that there _has_ to be
output because $a is set in fact.
Or am I wrong?
NULL == not set
-Andrei
Some people try to achieve immortality through their work, others
through their children. I hope to achieve immortality by not dying.
-- Woody Allen
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Re: [PHP-DEV] wrong implementation of isset()?
* Andrei Zmievski wrote:
?php
$a = NULL;
if (isset($a)) { print "ok, du hast recht"; }
?
Shouldn't this script generate some output? IMO $a is set
and isset() should return true.
NULL == not set
Great analysis. What about answering the question? Stanislav Malyshev
said some months ago this is 'strange', see the discussion around bug
6076. Tell us at least, why this actually isn't strange.
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Re: [PHP-DEV] wrong implementation of isset()?
On Tue, 06 Feb 2001, Bjoern Hoehrmann wrote: NULL == not set Great analysis. What about answering the question? Stanislav Malyshev said some months ago this is 'strange', see the discussion around bug 6076. Tell us at least, why this actually isn't strange. By default, any unset variable has value NULL - and isset(NULL) returns false to indicate that. Similarly, assigning NULL to a variable unsets it. -Andrei * The great thing about standards is that there are so many to choose from. * -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED]
Re: [PHP-DEV] wrong implementation of isset()?
On Tue, 6 Feb 2001 13:43:29 -0600, Andrei Zmievski wrote: On Tue, 06 Feb 2001, Bjoern Hoehrmann wrote: NULL == not set Great analysis. What about answering the question? Stanislav Malyshev said some months ago this is 'strange', see the discussion around bug 6076. Tell us at least, why this actually isn't strange. By default, any unset variable has value NULL - and isset(NULL) returns false to indicate that. Similarly, assigning NULL to a variable unsets it. But if I declare the variable in my script (and in the namespace), it's existing, no matter which value it has (String, Integer, NULL or whatever). As a result of that, isset() should return true. -Martin -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED]
RE: [PHP-DEV] wrong implementation of isset()?
null, adjective: having no value IMHO, isset() should be left as is. Either way if you are looking for a null value you will have to use '== NULL' or is_null(). if (isset($a) is_null($a)) if (isset($a)) if (is_null($a)) etc... The only possible situation I can think(right now) of where this might be useful is if you do not care that the value is null and null is a perfectly legal value(or non-value). In which case, all you are accomplishing is breaking everyone else's script who does not allow null values because they rely on isset() returning false and not letting these by. Chris -Original Message- From: Martin Jansen [mailto:[EMAIL PROTECTED]] Sent: Tuesday, February 06, 2001 2:19 PM To: Andrei Zmievski; Bjoern Hoehrmann Cc: PHP Development Mailing List Subject: Re: [PHP-DEV] wrong implementation of isset()? On Tue, 6 Feb 2001 13:43:29 -0600, Andrei Zmievski wrote: On Tue, 06 Feb 2001, Bjoern Hoehrmann wrote: NULL == not set Great analysis. What about answering the question? Stanislav Malyshev said some months ago this is 'strange', see the discussion around bug 6076. Tell us at least, why this actually isn't strange. By default, any unset variable has value NULL - and isset(NULL) returns false to indicate that. Similarly, assigning NULL to a variable unsets it. But if I declare the variable in my script (and in the namespace), it's existing, no matter which value it has (String, Integer, NULL or whatever). As a result of that, isset() should return true. -Martin -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED] -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED]
Re: [PHP-DEV] wrong implementation of isset()?
"Mark J. Hershenson" wrote: Great analysis. What about answering the question? Stanislav Malyshev said some months ago this is 'strange', see the discussion around bug 6076. Tell us at least, why this actually isn't strange. By default, any unset variable has value NULL - and isset(NULL) returns false to indicate that. Similarly, assigning NULL to a variable unsets it. -Andrei * The great thing about standards is that there are so many to choose from. * Well, sure, isset(NULL) should return false, it's not a variable set in the scope. A constant(?) yes, but not a variable. But if you set a variable at some point in a script, would it not stand to reason that that name is in the global/local namespace, and therefore IS set? Perhaps, in order to maintain compatibility, we should re-document is_set, create the documentation for is_null, and look into creating a new function that will determine if something has "ever been inside the namespace", regardless of its current value, or absence of value. Right now, the *documentation* for isset does imply that: $a = NULL; isset($a); //TRUE when this is not the case. Specifically, the documentation says "Returns true if a variable exists" rather than "Returns true if a variable exists, but has not been sunsequently assigned a value (or non-value) of NULL, and has not been unset(). -Ronabop -- Personal: [EMAIL PROTECTED], 520-326-6109, http://www.opus1.com/ron/ Work: [EMAIL PROTECTED], 520-546-8993, http://www.pnsinc.com/ The opinions expressed in this email are not neccesarrily those of myself, my employers, or any of the other little voices in my head. -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED]
Re: [PHP-DEV] wrong implementation of isset()?
On Wed, 7 Feb 2001, [ISO-8859-1] André Langhorst wrote: we should just define (and document) this similar to Andrei (note, I do not use the word "the same" I use that word equal, what means different things): NULL equals absence_of_value equals absence_of_variable_in_namespace I can imagine no case where people would need to differentiate between NULL and never been in namespace, we should not allow this, otherwise we would introduce the differentiation into a third state, non existent, what raises the wtf-factor and is not required as far as I can think andré I agree. I've watched a lot of seasoned programmers learning PHP and the behaviour of various functions operating on NULL, 0, and '' has always had an extremely high wtf-factor (I really like that term). Most of the former discrepancies have been fixed, though. Try as I might, I can't think of a good case where you'd want to check for NULL and existance in the namespace. -- John Donagher Application Engineer Intacct Corp. - Powerful Accounting on the Web 408-395-0989 720 University Ave. Los Gatos CA 95032 www.intacct.com Public key available off http://www.keyserver.net Key fingerprint = 4024 DF50 56EE 19A3 258A D628 22DE AD56 EEBE 8DDD -- PHP Development Mailing List http://www.php.net/ To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] To contact the list administrators, e-mail: [EMAIL PROTECTED]
Re: [PHP-DEV] wrong implementation of isset()?
Andr Langhorst wrote:
Perhaps, in order to maintain compatibility, we should re-document is_set,
create the documentation for is_null, and look into creating a new function
that will determine if something has "ever been inside the namespace", regardless
of its current value, or absence of value.
we should just define (and document) this similar to Andrei (note, I do
not use the word "the same" I use that word equal, what means different
things):
NULL equals absence_of_value equals absence_of_variable_in_namespace
I can imagine no case where people would need to differentiate between
NULL and never been in namespace
(Disclaimer: I think much of this is a bit silly, as it all can be
worked around, or people can avoid using NULL... but for the sake of
those who believe "NULL" should be a value)
Here's a possible case for this:
You have three forms. Each uses differently named variables.
All three post to the same page. One way a user might try to code
for this is:
if (isset($HTTP_POST_VARS[var_only_from_form_one]){ include ("foo");}
if (isset($HTTP_POST_VARS[var_only_from_form_two]){ include ("bar");}
Or using "has_ever-been_a_var" to do the same thing. Now, if one of those var's
has been assigned NULL somehow, their logic breaks, even though the var is
actually there, and has been set with something they consider a "value".
In a more interesting fashion, it adds a possible security feature,
where folks could actually error out their scripts if a user tried
to _introduce_ a faked variable, because it wasn't "supposed to be
there" under the current conditions, or at all. By walking the var arrays,
and checking against the expected vars, a user could send a security
warning if sombody was hacking a URL or faking a form the obvious
case I can think of is folks adding "debug=1" somehow.
-Ronabop
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The opinions expressed in this email are not necessarily those of myself,
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