php不想修改字段,php想实现一个字段被赋值后就不能修改了，这样怎么实现呢？...

php 本身没有类似C# readonly这样的修饰符&＃xff0c;应该要通过设计实现了吧

php没有提供这样的功能&＃xff0c;不过在面向对象的设计中&＃xff0c;可以通过set/get方法实现。

class {

private $a &＃61; null;

public function setA($a) {

if (null &＃61;&＃61;&＃61; $this->a) {

$this->a &＃61; $a;

}

}

public function getA() {

return $this->a;

}

}

对于set/get方法&＃xff0c;可以用__set/__get这两个魔术函数实现&＃xff0c;书写效果可以更佳。

常量不就行了吗&＃xff1f;

define(key,value)

Talk is cheap,i will show you the code demo.

Like this:

//1.first snippet

class HelloSomeOne{

const NAME &＃61; "PHP技术大全";

//todo something else.

}

//2. second snippet

//not in class body inner

const NAME &＃61; "PHP技术大全";

在PHP脚本里可以用define实现&＃xff0c;在PHP类里可以用const实现

&＃64;有明 正解, 但是只需要实现getter就可以了.

Yii

框架的

Object

就实现了这样的功能.

class Object

{

public function __get($name)

{

$getter &＃61; &＃39;get&＃39; . $name;

if (method_exists($this, $getter)) {

return $this->$getter();

} elseif (method_exists($this, &＃39;set&＃39; . $name)) {

throw new InvalidCallException(&＃39;Getting write-only property: &＃39; . get_class($this) . &＃39;::&＃39; . $name);

} else {

throw new UnknownPropertyException(&＃39;Getting unknown property: &＃39; . get_class($this) . &＃39;::&＃39; . $name);

}

}

/**

* Sets value of an object property.

*

* Do not call this method directly as it is a PHP magic method that

* will be implicitly called when executing &＃96;$object->property &＃61; $value;&＃96;.

* &＃64;param string $name the property name or the event name

* &＃64;param mixed $value the property value

* &＃64;throws UnknownPropertyException if the property is not defined

* &＃64;throws InvalidCallException if the property is read-only

* &＃64;see __get()

*/

public function __set($name, $value)

{

$setter &＃61; &＃39;set&＃39; . $name;

if (method_exists($this, $setter)) {

$this->$setter($value);

} elseif (method_exists($this, &＃39;get&＃39; . $name)) {

throw new InvalidCallException(&＃39;Setting read-only property: &＃39; . get_class($this) . &＃39;::&＃39; . $name);

} else {

throw new UnknownPropertyException(&＃39;Setting unknown property: &＃39; . get_class($this) . &＃39;::&＃39; . $name);

}

}

}

只要继承

Object

, 如果属性是只读的, 只需要实现getter, 如果是只写的, 只需要实现setter.

class Test extends Object

{

private $a &＃61; &＃39;read-only&＃39;;

public function getA()

{

return $this->a;

}

}