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Bug #39721 __autoload and inheritance causes data corruption
Submitted: 2006-12-03 16:52 UTC Modified: 2006-12-05 19:05 UTC
From: dlanoire at neuf dot fr Assigned: dmitry (profile)
Status: Closed Package: Class/Object related
PHP Version: 5.2.0 OS: Windows XP SP2
Private report: No CVE-ID: None
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 [2006-12-03 16:52 UTC] dlanoire at neuf dot fr
Description:
------------
__autoload() function causes data corruption when using inheritance. In my example, the value of $foo->instance is 2 and SHOULD BE 1 !
In test.php, if I comment the include_once of autoload.php and uncomment the include_file of classes, the value of $foo->instance is correct (=1). 
Why ? Normally, there is no difference between autoload and explicit class file inclusion ?

Reproduce code:
---------------
To test the bug, you need four files.
test.php :
<?php
include_once "autoload.php"; 
//include_once "test2.php";
//include_once "test2_child.php";

$foo = new test_oop();
$child = new test_oop_child();
echo $foo->instance . "<br>";
echo $child->instance . "<br>";
?>

test2.php :
<?php
class test_oop {
	private static $instances = 0;
	public $instance;
	
	public function __construct() {
		$this->instance = ++self::$instances;
	}
	 
} // class
?>

test2_child.php :
<?php
include_once "autoload.php"; 

class test_oop_child extends test_oop {
	 
} // class
?>

autoload.php :
<?php
function __autoload($className) {
	require_once $className . ".php";
} 
?>

Expected result:
----------------
$foo->instance = 1

Actual result:
--------------
$foo->instance = 2

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 [2006-12-03 17:04 UTC] dlanoire at neuf dot fr
Sorry, I made a mistake with the source code. The good one is :

test.php :
<?php
include_once "autoload.php"; 
//include_once "test2.php";
//include_once "test2_child.php";

$foo = new test2();
$child = new test2_child();
echo $foo->instance . "<br>";
echo $child->instance . "<br>";
?>

test2.php :
<?php
class test2 {
	private static $instances = 0;
	public $instance;
	
	public function __construct() {
		$this->instance = ++self::$instances;
	}
	 
} // class
?>

test2_child.php :
<?php
include_once "autoload.php"; 

class test2_child extends test2 {
	 
} // class
?>

autoload.php :
<?php
function __autoload($className) {
	require_once $className . ".php";
} 
?>
 [2006-12-04 17:04 UTC] dlanoire at neuf dot fr
To give you more inputs, if I replace the echo functions by var_dump, I notice that $foo->instance IS A REFERENCE, as you can see in my printout :

object(test2)#1 (1) {
  ["instance"]=>
  &int(2)
}
object(test2_child)#2 (1) {
  ["instance"]=>
  int(2)
}

Furthermore, if I replace "$child = new test2_child()" by "$child = new test2()", there is no bug with __autoload so I suppose thet the problem comes from inheritance ...
Hope that helps.
 [2006-12-04 17:28 UTC] dlanoire at neuf dot fr
fix summary
 [2006-12-05 19:05 UTC] dmitry@php.net
Fixed in CVS HEAD and PHP_5_2.
 
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