jQuery validation form issue

Question

I use the following code in order to know if some username is already present in my database. I'm using jquery validator, and I configure the script in this way:

$(document).ready(function(){

    // Validate
    // http://bassistance.de/jquery-plugins/jquery-plugin-validation/
    // http://docs.jquery.com/Plugins/Validation/
    // http://docs.jquery.com/Plugins/Validation/validate#toptions

        $('#profile').validate({
        rules: {
          name: {
            minlength: 2,
            required: true
          },
          username: {
            minlength: 2,
            required: true,
            remote: "../check-username.php"
          }
        },
            highlight: function(element) {
                $(element).closest('.control-group').removeClass('success').addClass('error');
            },
            success: function(element) {
                element
                .text('OK!').addClass('valid')
                .closest('.control-group').removeClass('error').addClass('success');
            }
      });

});

where check-username.php is defined as:

<?php 

require_once('connection.php');

$check = "true"; 
$request = trim(strtolower($_REQUEST['username'])); 

mysql_select_db($dbname, $temp);
  $query_username=sprintf("SELECT * FROM users WHERE username = '$request'");

  $resultUsers = mysql_query($query_username, $temp) or die(mysql_error());

   $usernameFound= mysql_num_rows($resultUsers);

   if ($usernameFound> 0) { 
    $check = "false"; 
} 


header("Content-type: application/json; charset=windows-1251");
$result = $_REQUEST['username'].'('.$check.')';
echo $result;

?>

All works good, except the recognition of already existing username. Maybe something is wrong in:

remote: "../check-username.php"

or in the php file itself.

Someone can help me?

EDIT 1:

Trying the @MHR code I obtain this:

In this case "user1" already exists in my database. So this is good, but I don't want that the output is written under my input.

Answer 1

http://docs.jquery.com/Plugins/Validation/Methods/remote

The documentation has a shiningly absent example of what the response must be but it hints at JSON:

The response is evaluated as JSON and must be true for valid elements, and can be any false, undefined or null for invalid elements, using the default message; or a string, eg. "That name is already taken, try peter123 instead" to display as the error message. For more examples, take a look the marketo demo and the milk demo.

My guess is that you should return "true" if it's valid and "false" if it isn;t:

$check = true; 
$request = trim(strtolower($_REQUEST['username'])); 
mysql_select_db($dbname, $temp);
  $query_username=sprintf("SELECT * FROM users WHERE username = '$request'");
  $resultUsers = mysql_query($query_username, $temp) or die(mysql_error());
   $usernameFound= mysql_num_rows($resultUsers);
   if ($usernameFound> 0) { 
    $check = false; 
} 
header("Content-type: application/json; charset=windows-1251");
if($check){
  $check = "true";
}else{
  $check = "User: ".$request." already exist, please choose another user name.";
}
$result = "\"".$check."\"";
echo $result;