Provides a unique identifier for each zval. Same zvals should have same identifier.

zval_id.php

<?php
/**
 * This is a hacky zval_id implementation.
 * It tries to be as fast as possible,
 * and can only detect unique arrays, leaving them
 * modified
 * When in doubt, assumes it's a new zval!
 * @param  mixed &$zval 
 * @return integer        
 */
function _zval_id_light(&$zval)
{
	static $id=0;
	if (is_array($zval))
	{
		if (isset($zval['___VISITED___']))
			return $zval['___VISITED___'];
		else
			return $zval['___VISITED___']=$id++;
	}
	else
		return $id++;
}
/**
 * This is a more accurate zval_id
 * implementation. for each new zval,
 * it compares it to all previously checked
 * zval and if they are the same, same id is returned.
 * @param  mixed &$zval 
 * @return integer
 */
function _zval_id_accurate(&$zval)
{
	static $zvals=[];
	static $ids=0;
	$backup=$zval;
	$zval="___VISITED___";
	foreach ($zvals as $k=>$v)
		if ($v==='___VISITED___')
		{
			$id=$k;
			break;
		}
	if (!isset($id))
		$id=$ids++;
	$zval=$backup;
	$zvals[$id]=&$zval;
	return $id;
}
function _zval_id(&$zval) {
	return _zval_id_accurate($zval);
}