<?php
use ApiUser;
use ServiceUser as User2;
class Application{
  public static function main(){
    self::registe();
    new User();
    new User2();
  }
  public static function registe(){
    spl_autoload_register("Application::loadClass");
  }
  public static function loadClass($class){
    $class=str_replace('\', '/', $class);
    $class="./".$class.".php";
    require_once $class;    
  }
}
Application::main();

<?php
namespace Api;

use ServiceLogin;
class User{
  public function __construct(){
    echo "User类<br/>";
    new Login();
    new Account();
  }
}

<?php
namespace Api;

class Account{
  public function __construct(){
    echo "Account类<br/>";
  }
}

<?php
namespace Service;

class Login{
  public function __construct(){
    echo "Login类<br/>";
  }
}

<?php
namespace Service;

class User{
  public function __construct(){
    echo "Service下的User类<br/>";
  }
}