Description:
------------
A memory leak occurs when array that contains a reference to $this is altered in the object's destructor.

The leak does not occur if:
 * the array does not contain $this
 * the array is not altered in the destructor
 * $this is removed from the array in the destructor

Affected PHP versions: https://3v4l.org/lHeRV
This gist (https://gist.github.com/jmalloc/b88752e391d464609339) also contains the script to reproduce.




Test script:
---------------
class MemoryLeak
{
    public function __construct()
    {
        $this->things[] = $this;
    }

    public function __destruct()
    {
        $this->things[] = null;
    }

    private $things = [];
}

ini_set('memory_limit', '10M');

for ($i = 0; $i < 100000; ++$i) {
    $obj = new MemoryLeak();
}

echo "Done";

Expected result:
----------------
Done

Actual result:
--------------
Fatal error: Allowed memory size of 10485760 bytes exhausted (tried to allocate 20480 bytes) in /Users/james/<snip>/leak.php on line 30