PHP 手冊
前一頁 | 章 19. Classes and Objects (PHP 5) | 下一頁

# Scope Resolution Operator (::)

The Scope Resolution Operator (also called Paamayim Nekudotayim) or in simpler terms, the double colon, is a token that allows access to static, constant, and overridden members or methods of a class.

When referencing these items from outside the class definition, use the name of the class.

Paamayim Nekudotayim would, at first, seem like a strange choice for naming a double-colon. However, while writing the Zend Engine 0.5 (which powers PHP 3), that's what the Zend team decided to call it. It actually does mean double-colon - in Hebrew!

範例 19-10. :: from outside the class definition

`<?php class MyClass { const CONST_VALUE = 'A constant value'; } echo MyClass::CONST_VALUE; ?>`

Two special keywords self and parent are used to access members or methods from inside the class definition.

範例 19-11. :: from inside the class definition

`<?php 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(); ?>`

When an extending class overrides the parents definition of a method, PHP will not call the parent's method. It's up to the extended class on whether or not the parent's method is called. This also applies to Constructors and Destructors, Overloading, and Magic method definitions.

範例 19-12. Calling a parent's method

`<?php class MyClass { protected function myFunc() { echo "MyClass::myFunc()\n"; } } class OtherClass extends MyClass { // Override parent's definition public function myFunc() { // But still call the parent function parent::myFunc(); echo "OtherClass::myFunc()\n"; } } $class = new OtherClass(); $class->myFunc(); ?>`

前一頁 | 內容 | 下一頁
Visibility | 上一層 | Static Keyword