Ajax

How to check whether the Username is available or not in JqeryAjax and PHP?

1) CheckUserName.php

 <script src="jquery-latest.js" type="text/javascript"></script>

<style type="text/css">
.no{color:red;}
.yes{color:blue;}
</style>
<script src="jquery-latest.js" type="text/javascript"></script>
<script>
    $(document).ready(function(){
        $('#Uname').blur(function(){
            var form_data = {
                querName:"queryVal",
                Uname:$(this).val()
            };
            $.ajax({
                type:"POST",
                url:"chechUserName.php",
                data:form_data,
                success:function(result)
                {
                    $('#message').html(result);
                }
            });
        });
    });
</script>

<form method="post" action="#">
<table>
    <tr>
        <td>Username</td><td><input type="text" name="Uname" id="Uname"></td><td><div id="message"></div></td>
    </tr>
</table>
</form>

2) chechUserName.php

<?php
$querName = $_REQUEST['querName'];
if($querName == 'queryVal')
{
    $querVal = $_REQUEST['Uname'];
    check_value($querVal);
}
function check_value($querVal)
{
    $arrayVal = array("sairam","manoj","balaji","govind");
    if(in_array($querVal,$arrayVal))
    {
        echo "<span class='no'> $querVal is not available </span>";
    }
    else
    {
        echo "<span class='yes'> Available </span>";
    }
}
?>