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[2004-12-28 20:27 UTC] sir dot gallahad at gmail dot com
Description:
------------
First of all. It's not a bug. It's a sugestion to give more stability to the engine.
When the Zend Engine reaches the end of a script page it cleans up the classes that have been created.
Nowadays it cleans up in the order the classes have been created.
I suggest that it would be a safer routine to destroy a class following a heap of objects (first in last out).
It would help some nesting routines, not mentioning the memory allocation.
Reproduce code:
---------------
<?
$ident = 0;
class Tag {
public $aVar;
function __construct( $pMe ) {
global $ident;
$this->aVar = $pMe;
echo str_repeat(" ",$ident)."[".$this->aVar."]<br>";
$ident++;
}
function __destruct() {
global $ident;
$ident--;
echo str_repeat(" ",$ident)."[/".$this->aVar."]<br>";
}
}
$v1 = new Tag("tag1");
$v2 = new Tag("tag2");
$v3 = new Tag("tag3");
echo '<br><br>';
?>
Expected result:
----------------
[tag1]
[tag2]
[tag3]
[/tag3]
[/tag2]
[/tag1]
Actual result:
--------------
[tag1]
[tag2]
[tag3]
[/tag1]
[/tag2]
[/tag3]
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Last updated: Sun Nov 23 07:00:01 2025 UTC |
I believe this is a bug in PHP's garbage collection. The ordering in which __destruct methods are called can be very important when objects contain instances of other objects as class variables. I have run into problems because of the simple order that PHP uses to call __destruct methods. The order in which objects are destroyed should be determined by the number of references left which point to the object (I believe Java does something like this). In general, the Zend engine should use something like the following algorithm for garbage collection: foreach (object left to destroy) { if(no references point at this object) { call object's __destruct method destroy object } } The only hole in this algorithm is that an object that contains a reference to itself will never be destroyed and cause an endless loop in the algorithm above. These types of objects should be destroyed last. The above algorithm can be easily modified to achieve this. Please address this issue with PHP garbage collection. Thanks!Hi, I wonder why it's being not addressed for such a long time. This seems an important bug to me. Consider: <?php class Index { var $user; function __destruct() { if ($GLOBALS['i']->user === $this) { // update preferences in DB } } } $i = new Index(); ?> This works counter-intuitive and $GLOBALS['i'] is UNSET at the time the __destruct is called. The destructor is supposed to be called BEFORE the object itself is destroyed. Please change the order to FILO.