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 a , property, or method of a class or one of its parents. Moreover, static properties or methods can be overriden via . constantstaticstaticlate static binding

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

It's possible to reference the class using a variable. The variable's value can not be a keyword (e.g. , and ). self``parent``static

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!

Voorbeeld: :: from outside the class definition

<?php
class MyClass {
    const CONST_VALUE = 'A constant value';
}

$classname = 'MyClass';
echo $classname::CONST_VALUE;

echo MyClass::CONST_VALUE;
?>

Three special keywords , and are used to access properties or methods from inside the class definition. self``parent``static

Voorbeeld: :: from inside the class definition

<?php
class MyClass {
    const CONST_VALUE = 'A constant value';
}

class OtherClass extends MyClass
{
    public static $my_static = 'static var';

    public static function doubleColon() {
        echo parent::CONST_VALUE . "\n";
        echo self::$my_static . "\n";
    }
}

$classname = 'OtherClass';
$classname::doubleColon();

OtherClass::doubleColon();
?>

When an extending class overrides the parent's 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 , , and method definitions. Constructors and DestructorsOverloadingMagic

Voorbeeld: 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();
?>

See also . some examples of static call trickery

Vorige ← Overloading Volgende Properties →

Scope Resolution Operator (::)

Scope Resolution Operator (::)

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