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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<sect1 xml:id="language.oop5.paamayim-nekudotayim" xmlns="http://docbook.org/ns/docbook">
<title>Scope Resolution Operator (::)</title>
<para>
The Scope Resolution Operator (also called Paamayim Nekudotayim) or in
simpler terms, the double colon, is a token that allows access to
<link linkend="language.oop5.static">static</link>,
<link linkend="language.oop5.constants">constant</link>, and overridden
properties or methods of a class.
</para>
<para>
When referencing these items from outside the class definition, use
the name of the class.
</para>
<para>
As of PHP 5.3.0, it's possible to reference the class using a variable.
The variable's value can not be a keyword (e.g. <literal>self</literal>,
<literal>parent</literal> and <literal>static</literal>).
</para>
<para>
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!
</para>
<example>
<title>:: from outside the class definition</title>
<programlisting role="php">
<![CDATA[
<?php
class MyClass {
const CONST_VALUE = 'A constant value';
}
$classname = 'MyClass';
echo $classname::CONST_VALUE; // As of PHP 5.3.0
echo MyClass::CONST_VALUE;
?>
]]>
</programlisting>
</example>
<para>
Two special keywords <varname>self</varname> and <varname>parent</varname>
are used to access properties or methods from inside the class definition.
</para>
<example>
<title>:: from inside the class definition</title>
<programlisting role="php">
<![CDATA[
<?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(); // As of PHP 5.3.0
OtherClass::doubleColon();
?>
]]>
</programlisting>
</example>
<para>
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 <link
linkend="language.oop5.decon">Constructors and Destructors</link>, <link
linkend="language.oop5.overloading">Overloading</link>, and <link
linkend="language.oop5.magic">Magic</link> method definitions.
</para>
<example>
<title>Calling a parent's method</title>
<programlisting role="php">
<![CDATA[
<?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();
?>
]]>
</programlisting>
</example>
</sect1>
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