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Doc Bug #19080 Docs not clear on the diff between isset() and array_key_exists()
Submitted: 2002-08-23 19:20 UTC Modified: 2002-08-28 12:25 UTC
From: andrey at webgate dot bg Assigned:
Status: Closed Package: Documentation problem
PHP Version: 4.2.2 OS: All
Private report: No CVE-ID: None
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 [2002-08-23 19:20 UTC] andrey at webgate dot bg 
 Hello,
this code :
<?php 
$a = array(1=>NULL);
var_dump($a);
var_dump(isset($a[1]));
var_dump(array_key_exists(1,$a));
?>
Produces this :
array(1) {
  [1]=>
  NULL
}
bool(false)
bool(true)

So for first time I see difference in the use of isset() and array_key_exists(). Many users (including me till 1 one ago) believe that they are equivalent and because isset() is shorter it is mostly used.
Should be there any notice in the docs about this issue?
This code is correct and the bug report was inspired by note to do this by jmcastagnetto.

Regards,
Andrey

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 [2002-08-28 12:25 UTC] kalowsky@php.net 
There is an example in the docs explaining the difference between this on the isset() page.
 [2003-10-03 08:35 UTC] mvivino at avaya dot com 
After being "bitten" by this one myself, I looked back at the documentation more carefully, and of course this is correct behavior, as noted in the thread above.

The one-line summary of the function's behavior is still (IMHO) wrong:  

>> Returns TRUE if var exists; FALSE otherwise.

Simply rewriting this as:

>> Returns TRUE if var exists and is not set to NULL; FALSE otherwise.

would make the behavior crystal clear, and might save a few other folks trouble in the future.
 
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