PHP 面向?qū)ο蠡A(chǔ)(接口，類)，php面向

介紹PHP面向?qū)ο蟮幕A(chǔ)知識

1. 接口的定義interface ,類定義class,類支持abstract和final修飾符，abstract修飾為抽象類，抽象類

不支持直接實(shí)例化，final修飾的類/方法不能被繼承/方法重寫.
2. 接口的實(shí)現(xiàn)通過implements,類繼承extends

  <span>interface</span><span> IShape{
    </span><span>function</span><span> draw_core();
  };

  </span><span>class</span> PathShape <span>implements</span><span> IShape{
    </span><span>public</span> <span>function</span><span> draw_core(){}
  }

  </span><span>class</span> Rectangle <span>extends</span><span> PathShape{
    </span><span>public</span> <span>function</span><span> draw_core(){
      </span><span>//</span><span>overide draw_core</span>
<span>    }
  }</span>

3.靜態(tài)變量和常量(static ,const )
a.常量聲明變量名前面不需要加美元修飾符$,靜態(tài)變量需要
b.兩者都通過類訪問，靜態(tài)變量方法時(shí)候需要在變量名前加$美元修飾符好

   <span>class</span><span> MyClass{
     </span><span>const</span><span> M_CONST_VALUE;
     </span><span>static</span> <span>$M_STATIC_VALUE</span><span>;
   }

   MyClass</span>::<span>M_CONST_VALUE ;
   MyClass</span>::<span>$M_STATIC_VALUE</span>;

c.常量聲明時(shí)候不支持訪問權(quán)限修飾符，不能在const前加public，常量默認(rèn)就是public。

   <span>const</span> M_CONST  ; <span>//</span><span>OK</span>
   <span>public</span> <span>const</span> M_CONST ; <span>//</span><span> throw exception</span>

4.類內(nèi)部訪問非靜態(tài)/常量變量和方法通過$this,訪問父類通過parent,在類內(nèi)部訪問靜態(tài)變量和方法可以通過
self,self本質(zhì)是指向該類也可以通過static訪問

   parent::method(); <span>//</span><span>父類方法</span>
   <span>$this</span>->method() ; <span>//</span><span>方法實(shí)例方法</span>
   self::<span>$static_value</span> ;<span>//</span><span>訪問靜態(tài)變量</span>
   <span>static</span>::<span>$static_value</span>;<span>//</span><span>同上</span>

5.static和self的區(qū)別在于self指的是解析上下文，也是是作用與當(dāng)前類，static指的是被調(diào)用
的類而不是包含類，典型的例子就是單例

 <span>abstract</span> <span>class</span><span> ParentClass{
   </span><span>public</span> <span>static</span> <span>function</span><span> createInstance(){
     </span><span>return</span> <span>new</span> <span>static</span><span>(); 
     </span><span>//</span><span>這里不能使用self,因?yàn)閟elf本意其實(shí)指向parentclass的
     //如果你使用了self，那么將拋出異常，提示抽象類無法實(shí)例化
     //而static并不直接指向parentclass而是作用與包含類
     //</span>
<span>   }
 }

 </span><span>class</span> ChildClass <span>extends</span><span> ParentClass{
   </span><span>//
</span> }

7.類中使用攔截器,PHP攔截器有__get,__set,__inset,__unset,__call，這里只關(guān)注geth和set攔截器

 __get(<span>$property</span><span>) 當(dāng)訪問未定義的屬性時(shí)候該方法被調(diào)用
 __set(</span><span>$property</span>,<span>$value</span><span>)當(dāng)給未定義的屬性賦值時(shí)被調(diào)用
 </span><span>class</span><span> MyClass{
    </span><span>public</span> <span>function</span> __get(<span>$property</span><span>){
       </span><span>echo</span> "Access __get"<span>;
       </span><span>if</span>(property_exists(<span>$this</span>,<span>$property</span><span>)){
          </span><span>return</span> <span>$this</span>-><span>$property</span><span>;
       }</span><span>else</span><span>{
         </span><span>return</span> "unknown"<span>;
       }
    }

    </span><span>public</span> <span>function</span> __set(<span>$property</span>,<span>$value</span><span>){
      </span><span>if</span>(!property_exists(<span>$this</span>,<span>$property</span><span>)){
       </span><span>$this</span>->Name = <span>$value</span>; <span>//</span><span>變量不存在就直接給$Name賦值</span>
<span>      }
    }
    
    </span><span>public</span> <span>$Name</span> = "visonme"<span>;
 };
 </span><span>//</span><span>訪問</span>
 <span>$obj</span>  = <span>new</span><span> MyClass();
 </span><span>$obj</span>->Name ; <span>//</span><span>直接訪問變量$Name</span>
 <span>$obj</span>->Password;<span>//</span><span>Password未定義，先訪問__get最后輸出unknown

 //-for __set</span>
 <span>$obj</span>->password = 'fz-visonme';<span>//</span><span>password不存在，那么將走_(dá)_setz最后給$Name賦值</span>
 <span>echo</span> <span>$obj</span>->Name ; <span>//</span><span> output: fz-visonme</span>

8.類構(gòu)造函數(shù)和析構(gòu)函數(shù):__construct, __destruct ,構(gòu)造函數(shù)實(shí)例化對象時(shí)候調(diào)用，多用于成員變量初始化工作，析構(gòu)在類銷毀時(shí)候調(diào)用，多用于收尾工作

<span>class</span><span> MyClass{
  </span><span>function</span><span> __construct(){}
  </span><span>function</span><span> __destruct(){}
}</span>

9.對象的復(fù)制通過clone，clone關(guān)鍵字使用“值復(fù)制"方式來產(chǎn)生一個(gè)新的對象,對于對象復(fù)制本身還是走引用復(fù)制的。

a.簡單類型賦值

<span>class</span><span> MyClass{
  </span><span>public</span> <span>$ID</span><span>;
};

</span><span>$a</span> = <span>new</span><span> MyClass;
</span><span>$a</span>->ID = 199<span>;
</span><span>$b</span> = <span>clone</span> <span>$a</span><span>;  
</span><span>echo</span> <span>$b</span>->ID;   <span>//</span><span> output: 199</span>

b.包含對象的復(fù)制

<span>class</span><span> Account{
  </span><span>public</span> <span>$RMB</span><span>;
};
</span><span>class</span><span> MyClass{
  </span><span>public</span> <span>$ID</span><span>;
  </span><span>public</span> <span>$AccountObj</span><span>;

  </span><span>public</span> <span>function</span> __construct(<span>$c</span><span>){
    </span><span>$this</span>->AccountObj = <span>$c</span><span>;
  }
};

</span><span>$a</span> = <span>new</span> MyClass(<span>new</span><span> Account());
</span><span>$a</span>->AccountObj->RMB= 199<span>;
</span><span>$b</span> = <span>clone</span> <span>$a</span><span>;
</span><span>echo</span> <span>$b</span>->AccountObj->RMB;   <span>//</span><span>output: 199</span>
<span>$a</span>->AccountObj->RMB = 100<span>;
</span><span>echo</span> <span>$b</span>->AccountObj->RMB;  <span>//</span><span>output: 100</span>
<span>
在clone后，</span><span>$a的AccountObj改變時(shí)候</span>，同時(shí)會(huì)影響到<span>$b</span>

這種結(jié)果顯然不是我們所期望的，我們所期望的是ab是兩個(gè)不存在任何關(guān)聯(lián)的獨(dú)立對象.

為了解決這個(gè)問題我么可以在類內(nèi)部實(shí)現(xiàn)__clone，當(dāng)我們在外面調(diào)用clone時(shí)候其內(nèi)部會(huì)調(diào)用類的__clonef方法，所以我們可以通過重寫__clone來達(dá)到對clone的控制.例如針對b例子的改造

<span>class</span><span> MyClass{
  </span><span>public</span> <span>$ID</span><span>;
  </span><span>public</span> <span>$AccountObj</span><span>;

  </span><span>public</span> <span>function</span> __construct(<span>$c</span><span>){
    </span><span>$this</span>->AccountObj = <span>$c</span><span>;
  }

  </span><span>//</span><span>__clone實(shí)現(xiàn)clone的控制
  //這里內(nèi)部同時(shí)對Account實(shí)現(xiàn)一次clone，這里就可以避免b例子中出現(xiàn)的問題</span>
  <span>public</span> <span>function</span><span> __clone(){
    </span><span>$this</span>->ID = 0 ; <span>//</span><span>將ID置為0，如果你需要的話</span>
    <span>$this</span>->AccountObj = <span>clone</span> <span>$this</span>-><span>AccountObj;
  }
};</span>

關(guān)于__clone方法我們需要知道，該方法是在被clone后的對象上調(diào)用，而不是在原始的對象上面運(yùn)行的，例如上b例子中

? $b = clone $a ; //執(zhí)行的過程： 基本復(fù)制對象$a ---> $b執(zhí)行__clone()?

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