File structure

Namespace

The namespace declaration of each PHP file in the TYPO3 Core shows where the file belongs inside TYPO3 CMS. The namespace starts with \TYPO3\CMS, then the extension name in UpperCamelCase, a backslash and then the name of the subfolder of Classes/, in which the file is located (if any). E.g. the file typo3/sysext/frontend/Classes/ContentObject/ContentObjectRenderer.php with the class ContentObjectRenderer is in the namespace \TYPO3\CMS\Frontend\ContentObject.

use statements can be added to this section.

Copyright Notice

TYPO3 is released under the terms of GNU General Public License version 2 or any later version. The copyright notice with a reference to the license text must be included at the top of every TYPO3 PHP class file. User files must have this copyright notice as well. Example:

<?php
declare(strict_types = 1);

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

 namespace Vendor\SomeExtension\SomeFolder;

The wording must not be changed/updated/extended, under any circumstances.

Namespace imports

Necessary PHP classes should be imported like explained in the TYPO3 Coding Standards, (based on PER-CS1.0 / PSR-12 at the time of this writing, transitioning towards PER-CS2.0):

use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Core\Utility\HttpUtility;
use TYPO3\CMS\Core\Cache\Backend\BackendInterface;

Put one blank line before and after import statements. Also put one import statement per line.

Class information block

The class information block provides basic information about the class in the file. It should include a description of the class. Example:

/**
 * This class provides XYZ plugin implementation.
 */

PHP class

The PHP class follows the class information block. PHP code must be formatted as described in chapter "PHP syntax formatting".

The class name is expected to follow some conventions. It must be identical to the file name and must be written in upper camel case.

The PHP class declaration looks like the following:

class SomeClass extends AbstractBackend implements BackendInterface
{
    // ...
}

Optional module execution code

Module execution code instantiates the class and runs its method(s). Typically this code can be found in eID scripts and old Backend modules. Here is how it may look like:

$someClass = GeneralUtility::makeInstance(SomeClass::class);
$someClass->main();

This code must appear after the PHP class.