php

<?php
class A
{
    function foo()
    {
        if (isset($this)) {
            echo ‘$this is defined (‘;
            echo get_class($this);
            echo ") ";
        } else {
            echo "$this is not defined. ";
        }
    }
}

class B
{
    function bar()
    {
        A::foo();
    }
}

$a = new A();
$a->foo();
A::foo();
$b = new B();
$b->bar();
B::bar();
?>

以上例程会输出：

$this is defined (a)
$this is not defined.
$this is defined (b)
$this is not defined.

php

原文：http://www.cnblogs.com/wxdzbc/p/5726446.html