Podręcznik PHP
Poprzedni	Rozdział 19. Classes and Objects (PHP 5)	Następny

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!

Przykład 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.

Przykład 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.

Przykład 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();
?>

Poprzedni	Spis treści	Następny
Visibility	Początek rozdziału	Static Keyword