对PHPstatic的理解-php教程-PHP中文网

对PHPstatic的理解

php中文网

发布： 2016-08-08 09:26:30

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最近看了下Yii2.0的源码，发现里面有很多new static() 和static::的语句，顺便做下记录
- 首先看下面代码

<code><span><span>class</span><span>A</span> {</span><span>public</span><span>static</span><span><span>function</span><span>get_self</span><span>()</span> {</span><span>return</span><span>new</span><span>self</span>();
    }

    <span>public</span><span>static</span><span><span>function</span><span>get_static</span><span>()</span> {</span><span>return</span><span>new</span><span>static</span>();
    }
}
<span><span>class</span><span>B</span><span>extends</span><span>A</span> {</span>}
<span>echo</span> get_class(B::get_self()); <span>// A</span><span>echo</span> get_class(B::get_static()); <span>// B</span><span>echo</span> get_class(A::get_static()); <span>// A</span></code>

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通过上面可以看出new static() 表示的调用的类，而new self() 表示的是声明的类

<code><span><span>class</span><span>A</span> {</span><span>const</span> TEST = <span>'testa'</span>;

    <span>public</span><span>static</span><span><span>function</span><span>test_static</span><span>()</span>{</span><span>echo</span><span>static</span>::TEST;
    }

    <span>public</span><span>static</span><span><span>function</span><span>test_self</span><span>()</span>
    {</span><span>echo</span><span>self</span>::TEST;
    }
}
<span><span>class</span><span>B</span><span>extends</span><span>A</span> {</span><span>const</span> TEST = <span>'testb'</span>;
}
<span>echo</span> B::test_static(); <span>//testb</span><span>echo</span> B::test_self(); <span>//testa</span></code>

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通过上面的观察可以得出一个结论，static和被调用的类相关，而self则和声明的类（self代码所在的类）相关。