This is my Script :
<script>
   $(function() {
       $("#yourFormId").validate({
          rules: {
              mobile: {
                  required: true,
                  mobile: true,
                  remote: {
                     url: "mobileajax.php",
                     type: "get"
                  }
              },
           },
          messages: {
             mobile: {
                required: "Please enter a valid mobile address",
                minlength: "Please enter proper mobile",
                remote:function(){
                    $('.result').html('mobile Already used.').addClass('messageboxerror').fadeOut(5000);
                },
            }
         },
         errorPlacement: function (error, element) {
            element.attr("placeholder", error.text());
         },
   });
}); 
</script>
This is Html file:
<form id="yourFormId" action="try.php" method="post">
   mobile No.<div class="result"></div>
    <input id="mobile" type="text" name="mobile" />
<input type="submit" value="submit">
Thsi is mobileajax.php
 <?php
    require "connect/connectOpen.php";
    $sql = "select mobile from tbl_user";
    $rsd = mysql_query($sql);
    $data = mysql_fetch_array($rsd); 
    $registeredEmail = array($data[0]);
    $requestedEmail  = $_REQUEST['mobile'];
    if( in_array($requestedEmail, $registeredEmail) ){
        echo 'false';
    } else {
        echo 'true';
    }
?>
Same things i was using for email match exist its works, but for mobile its did not work.not validate moile number from database, only same code works with email match.
 
     
    