php - jQuery.validator.addMethod check username - php

Question

I am new to php and jQuery, I have googled a day but couldn't solve the problem. I want to check if the username is taken or not, but what I got is "Username is Already Taken" no matter what I enter.
so here is my code:
$(document).ready(function(){
$('#registration-form').validate({
rules: {
username: {
required: true,
minlength: 3,
maxlength: 25,
letters: true,
checkUsername: true,
},
password: {
required: true,
minlength: 6,
maxlength: 12
},
confirmpassword: {
required: true,
minlength: 6,
maxlength: 12,
equalTo: "#password"
},
email: {
required: true,
email: true
},
country:{
required: true,
}
},
highlight: function(element) {
$(element).closest('.form-group').addClass('error');
$(element).removeClass("valid");
},
success: function(element) {
element
.addClass('valid')
.closest('.form-group').removeClass('error');
}
});
$(".close, #close").click(function() {
$("label.error").hide();
$(".error").removeClass("error");
$("input.valid").removeClass("valid");
});
$.validator.addMethod("letters", function(value, element) {
return this.optional(element) || value == value.match(/^[a-zA-Z_]+$/);
},"Letters and underscore only.");
$.validator.addMethod("checkUsername", function(value, element){
var response='';
$.ajax({
type: "POST",
url: 'checkname.php',
data:"username="+value,
async:false,
success:function(data){
response = data;
}
});
if(response == 0)
{
return true;
}
else
{
return false;
}
}, "Username is Already Taken");
});
Here is my checkname.php
<?php
include 'connect.php';
if (isSet($_POST['username'])) {
$username = mysql_real_escape_string($_POST['username']);
$check_for_username = mysql_query("SELECT * FROM user WHERE username='$username'");
if (mysql_num_rows($check_for_username)>0) {
echo "false";
} else {
echo "true";
}
}
?>
Please help me, I am so frustrated .....

Answer 1

You should be using the remote method, which has already been tested and proven for this exact purpose. There is no reason to reinvent something that's already been done.
rules: {
username: {
required: true,
minlength: 3,
maxlength: 25,
letters: true,
remote: { // value of 'username' field is sent by default
type: 'POST',
url: 'checkname.php'
}
}
....
Your checkname.php
include 'connect.php';
if (isSet($_POST['username']))
{
$username = mysql_real_escape_string($_POST['username']);
$check_for_username = mysql_query("SELECT * FROM user WHERE username='$username'");
if (mysql_num_rows($check_for_username) > 0)
{
echo json_encode("Username is Already Taken");
// you could even try something like this:
// echo json_encode($username . " is Already Taken");
}
else
{
echo "true";
}
}
NOTE: mysql_ has been deprecated in PHP and should be replaced with mysqli or pdo_mysql. See: php.net/manual/en/function.mysql-query.php
Also see: jQuery Validate remote method usage to check if username already exists