(PHP 5 >= 5.2.0)
spl_object_hash — Return hash id for given object
This function returns a unique identifier for the object. This id can be used as a hash key for storing objects or for identifying an object.
A string that is unique for each currently existing object and is always the same for each object.
Example #1 A spl_object_hash() example
$id = spl_object_hash($object);
$storage[$id] = $object;
When an object is destroyed, its hash may be reused for other objects.