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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.8 $ -->
<sect1 id="language.oop5.interfaces">
<title>Object Interfaces</title>
<para>
Object interfaces allow you to create code which specifies which methods a
class must implement, without having to define how these methods are
handled.
</para>
<para>
Interfaces are defined using the interface keyword, in the same way as a
standard class, but without any of the methods having their contents
defined.
</para>
<para>
All methods declared in an interface must be public, this is the nature of an
interface.
</para>
<sect2>
<title><literal>implements</literal></title>
<para>
To implement an interface, the <literal>implements</literal> operator is used.
All methods in the interface must be implemented within a class; failure to do
so will result in a fatal error. Classes may implement more than one interface
if desired by separating each interface with a comma.
</para>
<note>
<para>
A class cannot implement two interfaces that share function names, since
it would cause ambiguity.
</para>
</note>
</sect2>
<sect2>
&reftitle.examples;
<example>
<title>Interface example</title>
<programlisting role="php">
<![CDATA[
<?php
// Declare the interface 'iTemplate'
interface iTemplate
{
public function setVariable($name, $var);
public function getHtml($template);
}
// Implement the interface
// This will work
class Template implements iTemplate
{
private $vars = array();
public function setVariable($name, $var)
{
$this->vars[$name] = $var;
}
public function getHtml($template)
{
foreach($this->vars as $name => $value) {
$template = str_replace('{' . $name . '}', $value, $template);
}
return $template;
}
}
// This will not work
// Fatal error: Class BadTemplate contains 1 abstract methods
// and must therefore be declared abstract (iTemplate::getHtml)
class BadTemplate implements iTemplate
{
private $vars = array();
public function setVariable($name, $var)
{
$this->vars[$name] = $var;
}
}
?>
]]>
</programlisting>
</example>
<simpara>
See also the <link linkend="language.operators.type">instanceof</link>
operator.
</simpara>
</sect2>
</sect1>
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