php学习之旅：static变量与方法

static关键字用来修饰属性、方法，称这些属性、方法为静态属性、静态方法。

static的方法，只能访问static的属性，不能类访问非静态的属性。不过调用非静态方法不可以使用this关键字调用非静态方法，而必须使用self::关键字，并且被调用的非静态方法中不能有非静态变量，一般情况静态方法尽量不要调用非静态方法。

static的属性，在内存中只有一份，为所有的实例共用。

可以使用self:: 关键字访问当前类的静态成员。

非静态方法调用静态变量

<code><span><?php </span><span><span>class</span><span>test</span>{</span><span>public</span><span>static</span><span>$pi</span>=<span>3.14</span>;
        <span><span>function</span><span>display</span><span>()</span>
        {</span><span>return</span><span>self</span>::<span>$pi</span>;
        }   
    }
    <span>$test</span>=<span>new</span> test();
    <span>echo</span><span>'<br>'</span>.<span>$test</span>-&gt;display();
<span>?&gt;</span></span></code>

静态方法调用静态变量

<code><span><?php </span><span><span>class</span><span>test</span>{</span><span>public</span><span>static</span><span>$pi</span>=<span>3.14</span>;
        <span>static</span><span><span>function</span><span>display_static</span><span>()</span>
        {</span><span>return</span><span>self</span>::<span>$pi</span>;
        }   
    }
    <span>$test</span>=<span>new</span> test();
    <span>echo</span><span>'<br>'</span>.<span>$test</span>::display_static();
<span>?&gt;</span></span></code>

非静态方法调用静态方法

<code><span><?php </span><span><span>class</span><span>test</span>{</span><span>public</span><span>static</span><span>$pi</span>=<span>3.14</span>;
        <span>static</span><span><span>function</span><span>display_static</span><span>()</span>
        {</span><span>return</span><span>self</span>::<span>$pi</span>;
        }   
        <span><span>function</span><span>display</span><span>()</span>
        {</span><span>return</span><span>self</span>::display_static();
        }
    }
    <span>$test</span>=<span>new</span> test();
    <span>echo</span><span>'<br>'</span>.<span>$test</span>-&gt;display();
<span>?&gt;</span></span></code>

静态方法调用非静态方法（实际就相当于将非静态方法在调用过程中转变为静态方法来处理了）

<code><span><?php </span><span><span>class</span><span>test</span>{</span><span>public</span><span>static</span><span>$pi</span>=<span>3.14</span>;
        <span>static</span><span><span>function</span><span>display_static</span><span>()</span>
        {</span><span>return</span><span>self</span>::display();
        }   
        <span><span>function</span><span>display</span><span>()</span>
        {</span><span>return</span><span>self</span>::<span>$pi</span>;
        }
    }
    <span>$test</span>=<span>new</span> test();
    <span>echo</span><span>'<br>'</span>.<span>$test</span>::display_static();
<span>?&gt;</span></span></code>

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以上就介绍了php学习之旅：static变量与方法，包括了静态方法,静态属性,静态变量方面的内容，希望对PHP教程有兴趣的朋友有所帮助。