$('#submit').on('click', function (e) {
    e.stopPropagation();
    $.ajax({
      url: "../../controllers/Controller.php",
      data: {
        action: "LoginController/login",
        username: username,
        password: password
      },
      dataType: "text",
      type: 'POST',
      timeout: 10000,
      error: function () {
        alert("服务器超时");
      },
      success: function (data) {
          alert(data);
      }
    });
  });

<?php

if (!empty($_REQUEST['action'])) {
  try {
    $action = explode('/', $_REQUEST['action']);
    $class_name = $action[0];
    $method_name = $action[1];
    require $class_name . '.php';
    $class = new ReflectionClass($class_name);
    if (class_exists($class_name)) {
      if ($class->hasMethod($method_name)) {
        $func = $class->getmethod($method_name);
        $instance = $class->newInstance();
        $func->invokeArgs($instance, array($_REQUEST));
        $result = $instance->getResult();
        echo $result;
      }
    }
  } catch (Exception $exc) {
    echo $exc->getTraceAsString();
  }
}
?>

<?php
class LoginController {
　　
  private $result;
  function LoginController() {
    //初始化数据库连接等参数
  }
  function login($args) {
    //具体的登录逻辑
  }
  function getResult() {
    return $this->result;
  }
}
?>