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New basic oop5 documentation
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@166424 c90b9560-bf6c-de11-be94-00142212c4b1
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Curt Zirzow
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163
language/oop5/basic.xml
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163
language/oop5/basic.xml
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.1 $ -->
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<sect1 id="language.oop5.basic">
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<title>The Basics</title>
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<sect1 id="oop5.basic.class">
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<title>class</title>
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<para>
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Every class definition begins with the keyword class, followed by a class
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name, which can be any name that isn't a reserverd word in PHP. Followed
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by A pair of curly braces, of which contains the definition of the classes
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members and methods. Within each method, except for <link
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linkend="language.oop5.static">static</link> methods, a psudo variable
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<varname>$this</varname> is available. <varname>$this</varname> is a
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reference to the same instance that called the method.
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</para>
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<example>
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<title>Simple 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 SimpleClass {
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/* member declaration */
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public $var = 'a default value';
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/* method declaration */
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public function displayVar() {
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echo $this->var; /* Echo my own $var value */
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}
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}
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?>
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]]>
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</programlisting>
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</example>
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</sect1>
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<sect1 id="oop5.basic.new">
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<title>new</title>
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<para>
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To create an instance of an object, a new object must be created and
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assigned to a variable. An object will always be assigned when
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creating a new object unless the object has a <link
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linkend="language.oop5.decon">constructor</link> defined that throws an <link
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linkend="language.oop5.exceptions">exception</link> on error.
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</para>
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<example>
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<title>Creating an instance</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$instance = new SimpleClass()
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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 assigning an already created instance of an object to a new variable, the new variable
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will access the same instance as the object that was assigned. This
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behaviour is the same when passing instances to a function. A new instance
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of an already created object can be made by <link
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linkend="language.oop5.cloning">cloning</link> it.
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</para>
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<example>
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<title>Object Assignment</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$assigned = $instance;
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$reference =& $instance;
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$instance->var = '$assigned will have this value';
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$instance = null; /* $instance and $reference become null */
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var_dump($instance);
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var_dump($reference);
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var_dump($assigned);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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NULL
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NULL
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object(SimpleClass)#1 (1) {
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["var"]=>
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string(30) "$assigned will have this value"
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}
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]]>
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</screen>
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</example>
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</sect1>
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<sect1 id="oop5.basic.extend">
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<title>extend</title>
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<para>
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A class can inherit methods and members of another class by using the
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extend keyword in the declaration. It is not possible to extend multiple
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classes, a class can only inherit one base class.
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</para>
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<para>
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The inherited methods and members can be overloaded, unless the parent
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class has defined a method as <link
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linkend="language.oop5.final">final</link>, by redeclaring them
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within the same name defined in the parent class. It is possible to access the overloaded
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method or members by referencing them with <link
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linkend="lanuguage.oop5.paamayim-nekudotayim">parent::</link>
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</para>
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<example>
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<title>Simple Class Inherintance</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class ExtendClass extends SimpleClass {
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/* Redefine the parent method */
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function displayVar() {
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echo "Extending class\n";
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parent::displayVar();
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}
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}
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$extended = new ExtendClass();
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$extended->displayVar();
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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Extending class
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a default value
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]]>
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</screen>
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</example>
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</sect1>
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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:"../../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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