php - 我什么时候应该使用 'self' 而不是 '$this' ？

Question

在 PHP 5 中，使用 self 和 $this 有什么区别？

什么时候合适？

Answer 1

简答

Use $this to refer to the current object. Use self to refer to the current class. In other words, use $this->member for non-static members, use self::$member for static members.

完整答案

下面是$this和self对非静态和静态成员变量的正确用法示例:

<?php
class X {
    private $non_static_member = 1;
    private static $static_member = 2;

    function __construct() {
        echo $this->non_static_member . ' '
           . self::$static_member;
    }
}

new X();
?>

下面是 $this 和 self 对非静态和静态成员变量的不正确用法示例:

<?php
class X {
    private $non_static_member = 1;
    private static $static_member = 2;

    function __construct() {
        echo self::$non_static_member . ' '
           . $this->static_member;
    }
}

new X();
?>

下面是 polymorphism 的示例，其中 $this 用于成员函数:

<?php
class X {
    function foo() {
        echo 'X::foo()';
    }

    function bar() {
        $this->foo();
    }
}

class Y extends X {
    function foo() {
        echo 'Y::foo()';
    }
}

$x = new Y();
$x->bar();
?>

下面是一个抑制多态行为的示例，通过对成员函数使用 self:

<?php
class X {
    function foo() {
        echo 'X::foo()';
    }

    function bar() {
        self::foo();
    }
}

class Y extends X {
    function foo() {
        echo 'Y::foo()';
    }
}

$x = new Y();
$x->bar();
?>

The idea is that $this->foo() calls the foo() member function of whatever is the exact type of the current object. If the object is of type X, it thus calls X::foo(). If the object is of type Y, it calls Y::foo(). But with self::foo(), X::foo() is always called.

来自 http://www.phpbuilder.com/board/showthread.php?t=10354489 :

作者 http://board.phpbuilder.com/member.php?145249-laserlight