Mine

<?php
require('xajax/xajax_core/xajax.inc.php' );
//require('include/functions.php');
function favorite($username,$vid_id)
{
	global $conn_id;
	$faving = new xajaxResponse();
	//cheke  for variable
	if(empty($username) || empty($vid_id))
	{
		$faving->assign("favi", "innerHTML", "<a href=\"/register.php\"><img src=\"images/fav_add.gif\" title=\"add to favorite\"></a>");
	}
	// if all it's good
	elseif(!empty($username) && !empty($vid_id))
	{
		// cheke for user
		if($alors['nbr'] != 0){
			// cheke for fav data
			$sql  = "SELECT COUNT(*) AS nbr FROM pm_favorite WHERE username = '".$username."' and video = '".$vid_id."'";
			$res  = mysql_query($sql);
			$alors2  = mysql_fetch_assoc($res);
 
			if($alors2['nbr'] != 0){
 
				mysql_query("DELETE FROM pm_favorite WHERE username = '".$username."' and video = '".$vid_id."'");
				$faving->assign("favi", "innerHTML", "<a href=\"javascript:void(0)\" onClick=\"xajax_favorite($username,$vid_id); return false;\"><img src=\"images/fav_add.gif\" title=\"add to favorite\"></a>");
 
			}elseif($alors2['nbr'] == 0){
				mysql_query("INSERT INTO pm_favorite SET username = '".$username."',video = '".$vid_id."'");
				$faving->assign("favi", "innerHTML", "<a href=\"javascript:void(0)\" onClick=\"xajax_favorite($username,$vid_id); return false;\"><img src=\"images/fav_remove.gif\" title=\"add to favorite\"></a>");
			}
		}
	}
$faving->Alert("ok");
	return $faving;
}
$xajax = new xajax(); 
$xajax->registerFunction("favorite");
$xajax->processRequest();
?>
 
<html>
<head>
<title>test page </title>
<?php $xajax->printJavascript('xajax/');  ?>
</head>
 
<body>
 
<div id="favi"><a href="javascript:void(0)" onClick="xajax_favorite('lolol','loolol');">test</a></div>
 
</body>
</html>