PHP object-oriented - access modifiers
Jul 09, 2016 am 09:10 AMThere are three access modifiers in PHP, namely:
- public (public, default)
- protected (protected)
- private ( Private)
They can be used on the attributes and methods of a class respectively (the attributes and methods of a class are collectively called members of a class) to modify the access rights of class members.
public (public, default)
In PHP5, if a class does not specify an access modifier for a member, the default is public access.
<span style="color: #008000">/*</span><span style="color: #008000"> 以下兩個方法聲明訪問權(quán)限效果相同 </span><span style="color: #008000">*/</span> <span style="color: #0000ff">function</span><span style="color: #000000"> say(){}; publilc </span><span style="color: #0000ff">function</span> say(){};
When a member of a class is declared with a public access modifier, the member can be accessed and manipulated by external code.
private(private)
Members defined as private are visible to all members within the class and have no access restrictions. Access is not allowed outside the class.
protected
Protected is a little more complicated. Members declared as protected can only be accessed by subclasses of the class.
Access rights status table:
Access
|
public
|
protected |
private |
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All <span style="color: #000000">php </span><span style="color: #0000ff">class</span><span style="color: #000000"> Woman{ </span><span style="color: #0000ff">public</span> <span style="color: #800080">$name</span> = 'lisa'; <span style="color: #008000">//</span><span style="color: #008000"> 公共的訪問權(quán)限</span> <span style="color: #0000ff">protected</span> <span style="color: #800080">$money</span> = 3000.00; <span style="color: #008000">//</span><span style="color: #008000"> 受保護(hù)的權(quán)限</span> <span style="color: #0000ff">private</span> <span style="color: #800080">$age</span> = 35; <span style="color: #008000">//</span><span style="color: #008000"> 私有的訪問權(quán)限</span> <span style="color: #0000ff">function</span><span style="color: #000000"> printInfo(){ </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$this</span>-><span style="color: #000000">name; </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$this</span>-><span style="color: #000000">money; </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$this</span>-><span style="color: #000000">age; } </span><span style="color: #0000ff">private</span> <span style="color: #0000ff">function</span><span style="color: #000000"> secret(){ </span><span style="color: #0000ff">echo</span> "這是個秘密!"<span style="color: #000000">; } } </span><span style="color: #800080">$woman</span> = <span style="color: #0000ff">new</span><span style="color: #000000"> Woman(); </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$woman</span>->name; <span style="color: #008000">//</span><span style="color: #008000"> 公共屬性可以訪問 // echo $woman->money; // 受保護(hù)屬性,報致命錯誤 // echo $woman->age; // 私有屬性,報致命錯誤</span> <span style="color: #800080">$woman</span>->printInfo(); <span style="color: #008000">//</span><span style="color: #008000"> 可以打印三個屬性的信息,因為printInfo是公共方法 // $woman->secret(); // 私有方法,訪問出錯</span> <span style="color: #0000ff">class</span> Girl <span style="color: #0000ff">extends</span><span style="color: #000000"> Woman{ </span><span style="color: #008000">//</span><span style="color: #008000"> 可以重新定義父類的public和protected方法,但不能定義private的 // protected $money = 2000.00; // 可以從新定義</span> <span style="color: #0000ff">function</span><span style="color: #000000"> printInfo(){ </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$this</span>-><span style="color: #000000">name; </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$this</span>-><span style="color: #000000">money; </span><span style="color: #008000">//</span><span style="color: #008000"> echo $this->age; // 找不到屬性</span> <span style="color: #000000"> } } </span><span style="color: #800080">$girl</span> = <span style="color: #0000ff">new</span><span style="color: #000000"> Girl(); </span><span style="color: #0000ff">echo</span> <span style="color: #800080">$girl</span>->name; <span style="color: #008000">//</span><span style="color: #008000"> 公共屬性可以訪問 // echo $girl->money; // 受保護(hù)屬性,報致命錯誤 // echo $girl->age; // 私有屬性,找不到屬性</span> <span style="color: #800080">$girl</span>->printInfo(); <span style="color: #008000">//</span><span style="color: #008000"> 顯示$name,$money,找不到$age屬性;</span> ?> |
★ |
|
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Subclass |
★ |
★ |
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Within class |
★ |
★ |
★ |

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