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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 299619 $ -->
<sect1 xml:id="language.oop5.autoload" xmlns="http://docbook.org/ns/docbook">
<title>Autoloading Classes</title>
<para>
Many developers writing object-oriented applications create
one PHP source file per-class definition. One of the biggest
annoyances is having to write a long list of needed includes
at the beginning of each script (one for each class).
</para>
<para>
In PHP 5, this is no longer necessary. You may define an
__autoload function which is automatically
called in case you are trying to use a class/interface which hasn't been
defined yet. By calling this function the scripting engine is given
a last chance to load the class before PHP fails with an error.
</para>
<note>
<para>
Prior to 5.3.0, exceptions thrown in the __autoload function could not be
caught in the <link linkend="language.exceptions">catch</link> block and
would result in a fatal error. From 5.3.0+ exceptions thrown in the
__autoload function can be caught in the <link linkend="language.exceptions">
catch</link> block, with 1 provision. If throwing a custom exception, then
the custom exception class must be available. The __autoload function may
be used recursively to autoload the custom exception class.
</para>
</note>
<note>
<para>
Autoloading is not available if using PHP in CLI
<link linkend="features.commandline">interactive mode</link>.
</para>
</note>
<note>
<para>
If the class name is used e.g. in <function>call_user_func</function> then
it can contain some dangerous characters such as <literal>../</literal>.
It is recommended to not use the user-input in such functions or at least
verify the input in <function>__autoload</function>.
</para>
</note>
<para>
<example>
<title>Autoload example</title>
<para>
This example attempts to load the classes <literal>MyClass1</literal>
and <literal>MyClass2</literal> from the files <filename>MyClass1.php</filename>
and <filename>MyClass2.php</filename> respectively.
</para>
<programlisting role="php">
<![CDATA[
<?php
function __autoload($class_name) {
require_once $class_name . '.php';
}
$obj = new MyClass1();
$obj2 = new MyClass2();
?>
]]>
</programlisting>
</example>
<example>
<title>Autoload other example</title>
<para>
This example attempts to load the interface <literal>ITest</literal>.
</para>
<programlisting role="php">
<![CDATA[
<?php
function __autoload($name) {
var_dump($name);
}
class Foo implements ITest {
}
/*
string(5) "ITest"
Fatal error: Interface 'ITest' not found in ...
*/
?>
]]>
</programlisting>
</example>
<example>
<title>Autoloading with exception handling for 5.3.0+</title>
<para>
This example throws an exception and demonstrates the try/catch block.
</para>
<programlisting role="php">
<![CDATA[
<?php
function __autoload($name) {
echo "Want to load $name.\n";
throw new Exception("Unable to load $name.");
}
try {
$obj = new NonLoadableClass();
} catch (Exception $e) {
echo $e->getMessage(), "\n";
}
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
Want to load NonLoadableClass.
Unable to load NonLoadableClass.
]]>
</screen>
</example>
<example>
<title>Autoloading with exception handling for 5.3.0+ - Missing custom exception</title>
<para>
This example throws an exception for a non-loadable, custom exception.
</para>
<programlisting role="php">
<![CDATA[
<?php
function __autoload($name) {
echo "Want to load $name.\n";
throw new MissingException("Unable to load $name.");
}
try {
$obj = new NonLoadableClass();
} catch (Exception $e) {
echo $e->getMessage(), "\n";
}
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
Want to load NonLoadableClass.
Want to load MissingException.
Fatal error: Class 'MissingException' not found in testMissingException.php on line 4
]]>
</screen>
</example>
</para>
<simplesect role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>unserialize</function></member>
<member><link linkend="unserialize-callback-func">unserialize_callback_func</link></member>
<member><function>spl_autoload</function></member>
<member><function>spl_autoload_register</function></member>
</simplelist>
</para>
</simplesect>
</sect1>
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