I'm building a registration page that uses JQuery's validator plugin to validate the form. For the username, i used the remote method. So here's my jquery+html code: fiddle

And here's Available.php:

<?php 
    $usr = $_POST["username"];
    $link = new PDO('mysql:***;dbname=***;charset=UTF-8','***','***');
    $usr_check = $link->prepare("SELECT * FROM Conference WHERE Username = :usr");
    $link->bindParam(':usr', $usr);
    $usr_check->execute();
    if($usr_check->rowCount()>0)
        echo "false";
    else
        echo "true";
?>

So I have a test account in my database with the username: user. When I tried to submit my form with the same username, it didn't display the error saying "username taken" which means the php isn't correct. Any ideas where I went wrong? Thanks