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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.3 $ -->
<sect1 id="language.oop5.typehinting">
<title>Type Hinting</title>
<para>
PHP 5 introduces Type Hinting. Functions are now able to force parameters
to be objects (by specifying the name of the class in the function
prototype) or arrays (since PHP 5.1).
</para>
<example>
<title>Type Hinting examples</title>
<programlisting role="php">
<![CDATA[
<?php
// An example class
class MyClass
{
/**
* A test function
*
* First parameter must be an object of type OtherClass
*/
public function test(OtherClass $otherclass) {
echo $otherclass->var;
}
/**
* Another test function
*
* First parameter must be an array
*/
public function test_array(array $input_array) {
print_r($input_array);
}
}
// Another example class
class OtherClass {
public $var = 'Hello World';
}
?>
]]>
</programlisting>
<para>
Failing to satisfy the type hint results in a fatal error.
</para>
<programlisting role="php">
<![CDATA[
<?php
// An instance of each class
$myclass = new MyClass;
$otherclass = new OtherClass;
// Fatal Error: Argument 1 must be an object of class OtherClass
$myclass->test('hello');
// Fatal Error: Argument 1 must be an instance of OtherClass
$foo = new stdClass;
$myclass->test($foo);
// Fatal Error: Argument 1 must not be null
$myclass->test(null);
// Works: Prints Hello World
$myclass->test($otherclass);
// Fatal Error: Argument 1 must be an array
$myclass->test_array('a string');
// Works: Prints the array
$myclass->test_array(array('a', 'b', 'c'));
?>
]]>
</programlisting>
<para>
Type hinting also works with functions:
</para>
<programlisting role="php">
<![CDATA[
<?php
// An example class
class MyClass {
public $var = 'Hello World';
}
/**
* A test function
*
* First parameter must be an object of type MyClass
*/
function MyFunction (MyClass $foo) {
echo $foo->var;
}
// Works
$myclass = new MyClass;
MyFunction($myclass);
?>
]]>
</programlisting>
</example>
<para>
Type Hints can only be of the <type>object</type> and <type>array</type>
(since PHP 5.1) type. Traditional type hinting with <type>int</type> and
<type>string</type> isn't supported.
</para>
</sect1>
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