<?php
class A{
    public $data;
    public $obj;
    function __construct()
    {
        $this->data  = array();
        $this->obj   = new stdClass();
    }
    function __set($name, $value)
    {
        $this->data[$name] = $value;
        if (is_object($this->obj)) {
            $this->obj->$name = $value;
        }
    }
    function __get($name)
    {
        if (is_object($this->obj)) {
            return $this->obj->$name;
        }
    }
}
$a = new A();
$a->a = '123';
var_dump($a->a);   //123
echo "<br>";
var_dump(empty($a->a));  //true,为什么这里会是true？百思不得其解，bug？
echo "<br>";
$b = $a->a;
var_dump(empty($b));   //false
?>