php中this、self、parent解析

概述：

this:指向类当前对象的指针；self：指向类本身，一般指向类中的静态变量；parent：指向父类的指针，一般使用parent来调用父类的构造函数。

下面通过程序详细介绍：

1、this

<?php
class Model_this{
private $name;	//定义类私有成员
function __construct($name){			//PHP 5 允许定义构造函数和析构函数
$this->name = $name;
}
function __destruct(){}
function showName(){
echo $this->name."\n";
}
}
$obj_1 = new Model_this("Jim");
$obj_2 = new Model_this("Tom");
$obj_1->showName();	//输出Jim
$obj_2->showName();	//输出Tom
?>

this是在对象实例化的时候确定指向，指向类当前的对象。

2、self

<?php
class Model_self{
private static $num = 0;
private $sum;
function __construct(){
$this->sum = ++self::$num;
}
function showSum(){
echo $this->sum."\n";
}
}
$obj_3 = new Model_self();
$obj_3->showSum();		//输出1
$obj_4 = new Model_self();
$obj_4->showSum();		//输出2
?>

self和类的对象没有关系，它指向类本身。

3、parent

<?php
class BaseClass{
public $name;
function __construct($name){
$this->name = $name;
}
}
class SubClass extends BaseClass{
private $sex, $age;
function __construct($sex, $age){
parent::__construct("Jim");
$this->sex = $sex;
$this->age = $age;
}
function showInfo(){
echo $this->name." is a ".$this->sex;
echo " and ".$this->age." years old.\n";
}
}
$obj_jim = new SubClass("man", 23);
$obj_jim->showInfo();	//输出 Jim is a man and 23 years old.
?>

使用parent来调用父类的构造函数。