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PHP面向对象构造函数说明

WBOY

发布： 2016-07-30 13:30:03

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本文不再赘述面向对象的知识，本文着重说明PHP的构造函数。
php类的构造函数可以是魔术魔方__construct() 也可以是和类同名的函数，实例如下：

<code><span><span>class</span><span>A</span>{</span><span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...'</span>;
    } 
 }
 <span><span>class</span><span>B</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...'</span>;
    }
 }

 <span>$a</span> = <span>new</span> A();   <span>// A is constructing...</span><span>$b</span> = <span>new</span> B();   <span>// B is constructing...</span></code>

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此外，在继承时，应该注意的是：
【子类可以不写构造函数，那么使用父类的构造函数】

<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>;
    <span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>;
    }
    <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>;
    }
    <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name;
    }
 }
 <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>/*
    public function __construct(){
        echo 'B is contructing...<br>';
    }
    */</span> }

 <span>//$a = new A();</span><span>$b</span> = <span>new</span> B();  <span>// A is constructing...</span><span>$b</span>->set_name(<span>'zhangsan'</span>);
 <span>echo</span><span>$b</span>->get_name();</code>

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【子类如果写了构造函数，那么不会再调用父类的构造函数了】

<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>;
    <span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>;
    }
    <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>;
    }
    <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name;
    }
 }
 <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...<br>'</span>;
    }

 }

 <span>//$a = new A();</span><span>$b</span> = <span>new</span> B(); <span>// just echo 'B is contructing...'</span><span>$b</span>->set_name(<span>'zhangsan'</span>);
 <span>echo</span><span>$b</span>->get_name(); <span>// zhangsan</span></code>

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【父类的构造函数如果是私有的，可以被继承，但是子类必须有自己的构造函数，并且明确写出来】

<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>;
    <span>private</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>;
    }
    <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>;
    }
    <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name;
    }
 }
 <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...<br>'</span>;
    }

 }

 <span>//$a = new A();</span><span>$b</span> = <span>new</span> B(); <span>// B is contructing...</span><span>$b</span>->set_name(<span>'zhangsan'</span>);
 <span>echo</span><span>$b</span>->get_name();  <span>// zhangsan</span></code>

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以上就介绍了PHP面向对象构造函数说明，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。