#31326 [Com]: Object Destruction Order

ID: 31326 Comment by: ebenblues at yahoo dot com Reported By: sir dot gallahad at gmail dot com Status: No Feedback Bug Type: Zend Engine 2 problem Operating System: Linux PHP Version: 5.0.2 New Comment: 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! Previous Comments: ------------------------------------------------------------------------ [2005-03-20 18:05:49] sniper@php.net No feedback was provided. The bug is being suspended because we assume that you are no longer experiencing the problem. If this is not the case and you are able to provide the information that was requested earlier, please do so and change the status of the bug back to "Open". Thank you. ------------------------------------------------------------------------ [2005-02-28 21:05:52] sniper@php.net Please try using this CVS snapshot: http://snaps.php.net/php5-latest.tar.gz For Windows: http://snaps.php.net/win32/php5-win32-latest.zip ------------------------------------------------------------------------ [2004-12-28 20:27:18] 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 = $pMe; echo str_repeat("&nbsp;&nbsp;&nbsp;&nbsp;",$ident)."[".$this->aVar."]<br>"; $ident++; } function __destruct() { global $ident; $ident--; echo str_repeat("&nbsp;&nbsp;&nbsp;&nbsp;",$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] ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=31326&edit=1