PHP의 직렬화 사용법

<?php
/*
作者 : shyhero
*/
class Person{ //声明一个Person类
  public $age;
  private $name;
  protected $sex;
  public function __construct($age="",$name="",$sex=""){
   $this -> age = $age;
   $this -> name = $name;
   $this -> sex = $sex;
  }
  public function say(){
   return $this -> age." ".$this -> name." ".$this -> sex;
  }
  function __sleep(){ //指定串行化时能提取的成员属性,没有参数,但是必须返回一个数组
   $arr = array("age","name");
   return $arr;
  }
  function __wakeup(){ //指定反串行化时,提取出来的值
   $this -> sex = "woman";
  }
}

<?php
  require("./Person.class.php");
  $p = new Person(21,"du","man"); //定义Person类对象
  $pString = serialize($p);  //对对象进行串行化
  file_put_contents("./file.txt",$pString);//存到文件里