From: m dot adeelnawaz at ymail dot com
Operating system: Windows 7 / Linux
PHP version: 5.5.0
Package: Class/Object related
Bug Type: Bug
Bug description:$this can be changed using reference
Description:
------------
In an object method, $this must always be a reference to the caller
object.
Now $this can not be re-assigned but re-assigning is not the only way to
modify $this. The code below demonstrates another way to set $this to
something other than the caller object.
This is what happens. $this is a reference (or copy of the identifier) to
the caller object. After doing this
$a = &$this;
$a and $this are both pointing to the same reference to the object
identifier. So changing one of them (assigning them to something not by
reference) will change the reference for both of them.
After executing this line
$a = new a();
Both $a and $this start pointing to the reference of the identifier to the
newly created object. You can change $this's reference by setting $a (not
by reference) to any non-null variable or value.
Test script:
---------------
class a{}
class b{
function test(){
$a = &$this;
echo get_class($this).'<br/>';
echo get_class($a).'<br/>';
$a = new a();
echo get_class($this).'<br/>';
echo get_class($a).'<br/>';
}
}
$b = new b();
$b->test();
Expected result:
----------------
One of the following should happen when I run the code above.
1. The code should produce a fatal error on line 3 ($a = &$this;) saying
that referencing to $this is not allowed.
2. The code should allow me to create a reference to $this in $a but
assigning any non-null value to $a (not by reference) should produce a
fatal error saying that $a is a reference to $this so it should (first) be
assigned by reference to some variable / object other than current object.
3. The code should allow me to create a reference to $this in $a but then
the same rules should apply to $a as $this with one exception that $a can
be unset().
Actual result:
--------------
b
b
b
a
--
Edit bug report at https://bugs.php.net/bug.php?id=65160&edit=1
--
Try a snapshot (PHP 5.4):
https://bugs.php.net/fix.php?id=65160&r=trysnapshot54
Try a snapshot (PHP 5.3):
https://bugs.php.net/fix.php?id=65160&r=trysnapshot53
Try a snapshot (trunk):
https://bugs.php.net/fix.php?id=65160&r=trysnapshottrunk
Fixed in SVN: https://bugs.php.net/fix.php?id=65160&r=fixed
Fixed in release: https://bugs.php.net/fix.php?id=65160&r=alreadyfixed
Need backtrace: https://bugs.php.net/fix.php?id=65160&r=needtrace
Need Reproduce Script: https://bugs.php.net/fix.php?id=65160&r=needscript
Try newer version: https://bugs.php.net/fix.php?id=65160&r=oldversion
Not developer issue: https://bugs.php.net/fix.php?id=65160&r=support
Expected behavior: https://bugs.php.net/fix.php?id=65160&r=notwrong
Not enough info:
https://bugs.php.net/fix.php?id=65160&r=notenoughinfo
Submitted twice:
https://bugs.php.net/fix.php?id=65160&r=submittedtwice
register_globals: https://bugs.php.net/fix.php?id=65160&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=65160&r=php4
Daylight Savings: https://bugs.php.net/fix.php?id=65160&r=dst
IIS Stability: https://bugs.php.net/fix.php?id=65160&r=isapi
Install GNU Sed: https://bugs.php.net/fix.php?id=65160&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=65160&r=float
No Zend Extensions: https://bugs.php.net/fix.php?id=65160&r=nozend
MySQL Configuration Error: https://bugs.php.net/fix.php?id=65160&r=mysqlcfg
