gistfile1.php

function register()
{
    global $db;

    if (isset($_POST['username']) && isset($_POST['passwordMD5']) && isset($_POST['email']))
    {
        $username = mysql_real_escape_string($_POST['username']);
        $passwordMD5 = mysql_real_escape_string($_POST['passwordMD5']);
        $email = mysql_real_escape_string($_POST['email']);

        $db->query("SELECT username, email FROM users WHERE username=? OR email=?")->bind(1, $username)->bind(2, $email)->execute();
        if ($db->getTotalRows()) {
            $result = $db->fetch();
            $resultusername = $result['username'];
            $resultemail = $result['email'];
        }

        if ($username != $resultusername || $email != $resultemail) {
            $db->query("INSERT INTO users (username', 'password', 'email') VALUES (?, ?, ?)")->bind(1, $username)->bind(2, $passwordMD5)->bind(3, $email)->execute();
            header('Content-type: application/json');
            echo json_encode(array(
                'username'  => $username,
                'email'     => $email,
                'status'    => 'Registration Passed'
            ));
            return true;
        } else {
            header('Content-type: application/json');
            echo json_encode(array(
                'username'  => $username,
                'email'     => $email,
                'status'    => 'Registration Failed'
            ));
            return false;
        }
    }
    return false;
}