php访问控制（public protected private）

在php中对属性或方法的访问控制，是在前面加public private protected等关键字来实现的，public修饰的类成员可以在任何地方访问,private修饰的类成员只能够被自身访问，protected修饰的类成员能被自身或其子类访问。

<code><span><span><?php </span><span><span>class</span><span>test</span>{</span><span>public</span><span>$public</span>=<span>'public'</span>;
        <span>private</span><span>$private</span>=<span>'private'</span>;
        <span>protected</span><span>$protected</span>=<span>'protected'</span>;

        <span>public</span><span><span>function</span><span>show</span><span>()</span>{</span><span>echo</span><span>$this</span>-><span>private</span>;
        }

        <span>public</span><span><span>function</span><span>show2</span><span>()</span>{</span><span>echo</span><span>$this</span>-><span>protected</span>;
        }
    }
    <span>$test</span>=<span>new</span> test();
    <span>echo</span><span>$test</span>-><span>public</span>;
    <span>$test</span>->show(); 
    <span>$test</span>->show2();
    <span>// exit();</span><span>// echo $test->protected;  //会产生一个致命错误</span><span>// echo $test->private;    //也会产生一个致命错误 private属性只能在定义的类中访问</span><span>/**
    * 
    */</span><span><span>class</span><span>test2</span><span>extends</span><span>test</span>
    {</span><span>//重写父类的show()方法</span><span><span>function</span><span>show</span><span>()</span>{</span><span>//继承自父类的protected</span><span>echo</span><span>$this</span>-><span>protected</span>;
        }
    }

    <span>$test2</span>=<span>new</span> test2();
    <span>echo</span><span>"<hr>"</span>;
    <span>// $test2->protected; //会产生一个致命错误  protected属性不能在外部访问</span><span>$test2</span>->show();  <span>//能够访问 protected只能被自身或其子类访问</span><span>?></span></span></span></code>

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