注册表单失败PHP AJAX

在ajax响应中返回多个错误是很麻烦的，如果多个错误被响应，1&2例如变为12。在数组中返回响应数据的最佳方式是什么？任何帮助都将不胜感激，提前表示感谢。

这是将表单张贴到PHP验证器的函数

$("document").ready(function() {
    $("#btn-signup").click(function() {
        var first_name = $("#fname_up").val();
        var last_name = $("#lname_up").val();
        var vemail = $("#email_up").val();
        var password = $("#password_up").val();
        var cpassword = $("#cpassword_up").val();
        var dataString = 'firstname='+first_name+'&lastname='+last_name+'&email='+vemail+'&password='+password+'&cpassword='+cpassword;
        $.ajax({
            type: "POST",
            url: "-signup.php",
            data: dataString,
            success: function(response){
                if (response == 1) {
                    console.log("1");
                }
                if (response == 2) {
                    console.log("2");
                }
                if (response == 3) {
                    console.log("3");
                }
                if (response == 4) {
                    console.log("4");
                }
                if (response == 5) {
                    console.log("5");
                }
                if (response == 6) {
                    console.log("6");
                }
                if (response == 7) {
                    console.log("7");
                }
                if (response == 12) {
                    console.log("You got to here");
                }
            }
        });
    return false;
    });
});

这是PHP表单验证器。

<?php
session_start();
require_once "database.php";
db_connect();
$errors = array();
// If request is a form submission
if($_SERVER['REQUEST_METHOD'] == 'POST'){
  // Validation
  // Check first_name is non-blank
  if(0 === preg_match("/'S+/", $_POST['firstname'])){
    echo "1";
  }
  // Check last_name is non-blank
  if(0 === preg_match("/'S+/", $_POST['lastname'])){
    echo "2";
  }
  // Check email is valid (enough)
  if(0 === preg_match("/.+@.+'..+/", $_POST['email'])){
    echo "3";
  }
  // Check password is valid
  if(0 === preg_match("/.{6,}/", $_POST['password'])){
    echo "4";
  }
  // Check password confirmation_matches
  if(0 !== strcmp($_POST['password'], $_POST['cpassword'])){
    echo "5";
  }
  // If no validation errors
  if(0 === count($errors)){
    // Sanitize first, last, and email
    $firstname = mysql_real_escape_string($_POST['firstname']);
    $lastname  = mysql_real_escape_string($_POST['lastname']);
    $email      = mysql_real_escape_string($_POST['email']);
    $password      = mysql_real_escape_string($_POST['password']);
    $cpassword     = mysql_real_escape_string($_POST['cpassword']);
    // Generate pseudo-random salt
    $salt = sha1(microtime() . $_POST['password']);
    // Generate password from salt
    $password = sha1($salt . $_POST['password']);

    // Insert user into the database
    $query = "INSERT INTO.......
    $result = mysql_query($query);
    if(mysql_errno() === 0){
      // Registration successful
      $user_id = mysql_insert_id();
      log_in($user_id);
      echo "9";
    } else if (preg_match("/^Duplicate.*email.*/// get rid of the two lines beforei", mysql_error())){
      echo "10";
    }  
  }
}