范围解析操作符(也可称作 Paamayim Nekudotayim)或者更简单地说是一对冒号,可以用于访问静态成员、方法和常量,还可以用于访问被覆盖类中的成员和方法。
当在类的外部访问这些静态成员、方法和常量时,必须使用类的名字。
把 Paamayim Nekudotayim 在希伯莱文就是双冒号的意思。
在类的外部使用 :: 操作符
class MyClass {
const CONST_VALUE = 'A constant value';
}
echo MyClass::CONST_VALUE;
self 和 parent 这两个特殊的关键字是用于在类的内部对成员或方法进行访问的。
例子:
class OtherClass extends MyClass
{
public static $my_static = 'static var';
public static function doubleColon() {
echo parent::CONST_VALUE . " n";
echo self::$my_static . " n";
}
}
OtherClass::doubleColon();
当一个子类覆盖其父类中的方法时,PHP 不会再执行父类中已被覆盖的方法,直到子类中调用这些方法为止。(是不是废话?不是,这是PHP与其他主流语言的一点区别)。这种机制也作用于构造函数和析构函数、重载及魔术函数。
class MyClass
{
protected function myFunc() {
echo "MyClass::myFunc() n";
}
}
class OtherClass extends MyClass
{
// 覆盖父类中的方法
public function myFunc()
{
// 但仍然可以调用已被覆盖的方法
parent::myFunc();
echo "OtherClass::myFunc() n";
}
}
$class = new OtherClass();
$class->myFunc();
--------------------------------------------------------------------------------
??重点??访问静态方法或者成员时一定要使用类名::的方式。
另外就是注意:PHP不会主动调用父类的方法,包括构造函数和析构函数在内。
参见这个文字:http://163xiaofan.blog.163.com/blog/static/1713578020061027101820973

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