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Request #28176 isset() returns false for properties returned from __get()
Submitted: 2004-04-27 03:57 UTC Modified: 2006-04-03 12:43 UTC
Votes:3
Avg. Score:5.0 ± 0.0
Reproduced:3 of 3 (100.0%)
Same Version:2 (66.7%)
Same OS:2 (66.7%)
From: benjcarson at digitaljunkies dot ca Assigned:
Status: Closed Package: Feature/Change Request
PHP Version: 5.0.* OS: *
Private report: No CVE-ID: None
View Developer Edit
 [2004-04-27 03:57 UTC] benjcarson at digitaljunkies dot ca 
Description:
------------
isset() returns false for variables that are returned using the __get() method, even though the variables are set and their values are returned properly.

Reproduce code:
---------------
<?php

class Foo { var $arr; function __get($var) { return $this->arr[$var]; } }
class Bar { var $var; function __get($tmp) { return $this->var; } }

$f = new Foo();
$f->arr["key"] = "val";

var_dump($f->key);           // Value returned correctly
var_dump(isset($f->key));    // isset() disagrees

$b = new Bar();
$b->var = "blah";

var_dump($b->dummy);         // Value returned correctly
var_dump(isset($b->dummy));  // isset() returns false
?>

Expected result:
----------------
string(3) "val"
bool(true)
string(4) "blah"
bool(true)


Actual result:
--------------
string(3) "val"
bool(false)
string(4) "blah"
bool(false)

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 [2004-04-27 08:31 UTC] derick@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

This is correct behavior, isset() does not call the __get and __set handlers.
 [2004-04-27 08:42 UTC] amt@php.net 
Hum. I think it's a good idea to modify isset() to call 
__get() and __set().

Otherwise, it breaks the principle of encapsulation. As 
a user of the class, I'm not supposed to know/care if 
I'm accessing the properties directly or if the 
developer has overloaded the property handler.

Besides, how else as a user can I check if a property is 
set if I can't use isset()?
 [2004-04-27 17:30 UTC] benjcarson at digitaljunkies dot ca 
It may come as no surprise, but I figure I should also mention it here for completeness: empty() displays the same behaviour--it does not call __get() either and returns true for variables that are set and retrieved via __get().

Obviously I agree with amt at php.net and think these are bugs.   For now, I'm working around this with:

!is_null($f->key);

From a user's point of view, the fact that this works and isset()/empty() do not is inconsistent.  Of course, knowing that isset()/empty() are language constructs and is_null() a function explains the behaviour, but I still think it is incorrect.
 [2004-05-10 03:15 UTC] helly@php.net 
We'd need a new handler. Say __exists($name). But not before 5.0 is out.
 [2006-04-03 12:43 UTC] tony2001@php.net 
We do have them since 5.1:
bool __isset ( string name )
void __unset ( string name )
 
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