check user using ajax

<?php $strcnn=mysql_connect("localhost","root",""); mysql_select_db("data",$strcnn);
$user=$_POST['user']; $pass=$_POST['pass'];
$strq="select * from tbluser where user='$user' AND pass='$pass'";
$result=mysql_query($strq); echo mysql_num_rows($result);
if(mysql_num_rows($result)<>0) { echo "helo:".$user; } else { echo "<a href='bai141.php'> quay lai</a>"; } ?>