php man page for spl_object_hash

SPL_OBJECT_HASH(3)							 1							SPL_OBJECT_HASH(3)

spl_object_hash - Return hash id for given object

SYNOPSIS
       string spl_object_hash (object  $obj)

DESCRIPTION
	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, as long as the object is not destroyed. Once the object is destroyed, its hash may be reused for other objects.

PARAMETERS
	      o $object
		- Any object.

RETURN VALUES
	A string that is unique for each currently existing object and is always the same for each object.

EXAMPLES
       Example #1

	      A spl_object_hash(3) example

	      <?php
	      $id = spl_object_hash($object);
	      $storage[$id] = $object;
	      ?>

NOTES
       Note

	       When an object is destroyed, its hash may be reused for other objects.

PHP Documentation Group 													SPL_OBJECT_HASH(3)