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The word "parents" in "When an extending class overrides the parents definition of a method, PHP will not call the parent's method." needs to be changed to "parent's". Closes GH-1389.
143 lines
3.5 KiB
XML
143 lines
3.5 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<sect1 xml:id="language.oop5.paamayim-nekudotayim" xmlns="http://docbook.org/ns/docbook">
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<title>Scope Resolution Operator (::)</title>
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<para>
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The Scope Resolution Operator (also called Paamayim Nekudotayim) or in
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simpler terms, the double colon, is a token that allows access to
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<link linkend="language.oop5.static">static</link>,
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<link linkend="language.oop5.constants">constant</link>, and overridden
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properties or methods of a class.
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</para>
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<para>
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When referencing these items from outside the class definition, use
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the name of the class.
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</para>
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<para>
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It's possible to reference the class using a variable.
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The variable's value can not be a keyword (e.g. <literal>self</literal>,
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<literal>parent</literal> and <literal>static</literal>).
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</para>
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<para>
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Paamayim Nekudotayim would, at first, seem like a strange choice for
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naming a double-colon. However, while writing the Zend Engine 0.5
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(which powers PHP 3), that's what the Zend team decided to call it.
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It actually does mean double-colon - in Hebrew!
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</para>
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<example>
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<title>:: from outside the class definition</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MyClass {
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const CONST_VALUE = 'A constant value';
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}
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$classname = 'MyClass';
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echo $classname::CONST_VALUE;
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echo MyClass::CONST_VALUE;
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?>
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]]>
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</programlisting>
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</example>
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<para>
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Three special keywords <varname>self</varname>, <varname>parent</varname> and
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<varname>static</varname> are used to access properties or methods from inside
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the class definition.
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</para>
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<example>
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<title>:: from inside the class definition</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class OtherClass extends MyClass
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{
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public static $my_static = 'static var';
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public static function doubleColon() {
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echo parent::CONST_VALUE . "\n";
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echo self::$my_static . "\n";
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}
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}
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$classname = 'OtherClass';
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$classname::doubleColon();
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OtherClass::doubleColon();
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?>
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]]>
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</programlisting>
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</example>
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<para>
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When an extending class overrides the parent's definition of a method,
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PHP will not call the parent's method. It's up to the extended class
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on whether or not the parent's method is called. This also applies to <link
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linkend="language.oop5.decon">Constructors and Destructors</link>, <link
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linkend="language.oop5.overloading">Overloading</link>, and <link
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linkend="language.oop5.magic">Magic</link> method definitions.
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</para>
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<example>
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<title>Calling a parent's method</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MyClass
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{
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protected function myFunc() {
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echo "MyClass::myFunc()\n";
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}
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}
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class OtherClass extends MyClass
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{
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// Override parent's definition
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public function myFunc()
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{
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// But still call the parent function
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parent::myFunc();
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echo "OtherClass::myFunc()\n";
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}
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}
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$class = new OtherClass();
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$class->myFunc();
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?>
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]]>
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</programlisting>
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</example>
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<para>
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See also <link linkend="language.oop5.basic.class.this">some examples of
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static call trickery</link>.
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</para>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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