PHP物件導向建構函數說明

本文不再贅述物件導向的知識，本文著重說明PHP的建構子。
php類別的建構子可以是魔術魔術方塊__construct() 也可以是和類別同名的函數，實例如下：

<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>

此外，在繼承時，應該注意的是：
【子類別可以不寫建構函數，那麼使用父類別的建構子】

<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>

【子類別如果寫了建構函數，那麼就不會再呼叫父類別的建構子了】

<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>

【父類別的建構子如果是私有的，可以被繼承，但是子類別必須有自己的建構函數，並且明確寫出來】

<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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以上就介紹了PHP物件導向建構函數說明，包含了面向的內容，希望對PHP教學有興趣的朋友有幫助。