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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.
As of PHP 5.3.0, it's possible to reference the class using a variable.
Keywords like self, parent or
static are not allowed in dynamic class references.
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!
Example 10.12. :: from outside the class definition
<?php
class MyClass {
const CONST_VALUE = 'A constant value';
}
$classname = 'MyClass';
echo $classname::CONST_VALUE;
echo MyClass::CONST_VALUE;
?>
Two special keywords self and parent
are used to access members or methods from inside the class definition.
Example 10.13. :: 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";
}
}
$classname = 'OtherClass';
echo $classname::doubleColon();
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.
Example 10.14. 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();
?>