如何在B类方法中调用A类方法,并使B类方法和参数从A类方法中可用?

类用户 {

  private $_var_1 = 10;
  private $_var_2 = 20;

  private function _preExecute() {
    //do something here before executing sub-class's method
  }

  private function _postExecute() {
    //do something here after executing sub-class's method
  }

  private function _anyMethod() {
    echo "Hello!";
  }

  public function execute($action) {
    $this->_preExecute();
    $obj = new __CLASS__."_".$action;
    $obj->execute();
    $this->_postExecute();
  }

}

class User_Add 
{

  public function execute() {
    echo $this->_var1;
    echo $this->_var2;
    parent::_anyMethod();
  }

}

$user = new User();
$user->execute("Add");

所以,正如您所看到的,我希望能够从类用户添加中访问用户类的变量和方法,这在php 5.2或更高版本中是可能的吗?