Checking username availability with ajax using jQuery
//use ajax to run the check
    $.post("check_username.php", { username: username },
        function(result){ alert(result);
            //if the result is 1
            if(result == 1){
                //show that the username is available
                $('#username_availability_result').html(username + ' is Available');
            }else{
                //show that the username is NOT available
                $('#username_availability_result').html(username + ' is not Available');
            }
    });