$item = explode("_", stripslashes($_REQUEST['item']));
	$x = 0;
	$_SESSION['level'] = 4;
	if($x <= count($_SESSION['level'])) {
		$i .= $_REQUEST['item'].'_';
		}

--------------

//$_REQUEST['item'] = '1_1_1_1_1_1_1_1_1';

$item = explode("_", $_REQUEST['item']);
$_SESSION['level'] = 4;

for( $i=0 $i < $_SESSION['level']; $i++ ) {
   $i .= $item[$i]."_";
}

//this will leave you with 1_1_1_1_

//this removes the trailing _
$i = substr($i, 0, -1);