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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<sect1 xml:id="language.oop5.inheritance" xmlns="http://docbook.org/ns/docbook">
<title>Object Inheritance</title>
<para>
Inheritance is a well-established programming principle, and PHP makes use
of this principle in its object model. This principle will affect the way
many classes and objects relate to one another.
</para>
<para>
For example, when you extend a class, the subclass inherits all of the
public and protected methods from the parent class. Unless a class overrides
those methods, they will retain their original functionality.
</para>
<para>
This is useful for defining and abstracting functionality, and permits the
implementation of additional functionality in similar objects without the
need to reimplement all of the shared functionality.
</para>
<sect2 xml:id="language.oop5.inheritance.examples">
<example xml:id="language.oop5.inheritance.examples.ex1">
<title>Inheritance Example</title>
<programlisting role="php">
<![CDATA[
<?php
class foo
{
public function printItem($string)
{
echo 'Foo: ' . $string . PHP_EOL;
}
public function printPHP()
{
echo 'PHP is great.' . PHP_EOL;
}
}
class bar extends foo
{
public function printItem($string)
{
echo 'Bar: ' . $string . PHP_EOL;
}
}
$foo = new foo();
$bar = new bar();
$foo->printItem('baz'); // Output: 'Foo: baz'
$foo->printPHP(); // Output: 'PHP is great'
$bar->printItem('baz'); // Output: 'Bar: baz'
$bar->printPHP(); // Output: 'PHP is great'
?>
]]>
</programlisting>
</example>
</sect2>
</sect1>
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Local variables:
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sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->
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