Object interfaces allow you to create code which specifies which methods a
class must implement, without having to define how these methods are
handled.
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.
All methods declared in an interface must be public, this is the nature of an
interface.
To implement an interface, the implements 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.
Example 19-18. Interface example
<?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;
}
}
?>
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See also the instanceof
operator.