File structure

TYPO3 files use the following structure:

  1. Opening PHP tag (including strict_types declaration)
  2. Namespace
  3. Copyright notice
  4. Included files
  5. Class information block in phpDoc format
  6. PHP class
  7. Optional module execution code

The following sections discuss each of these parts.

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.

Included files

Files are included using the require_once() function. All TYPO3 files must use absolute paths in calls to require_once(). There are two ways to obtain the path to the included file:

  1. Use one of the predefined TYPO3 constants: PATH_typo3 or PATH_site. The first one contains the absolute path to the corresponding TYPO3 directory. The last constant contains the absolute path to the TYPO3 root directory. Example:

    require_once(PATH_typo3 . 'sysext/frontend/Classes/Plugin/AbstractPlugin.php');
    
  2. Use the ExtensionManagementUtility::extPath() function. This function accepts two arguments: first the extension key and second the path to the included file inside the extension. The second argument is optional but recommended to use. Examples:

    require_once(ExtensionManagementUtility::extPath('lang', 'Classes/LanguageService.php'));
    require_once(ExtensionManagementUtility::extPath('lang') . 'Classes/LanguageService.php');
    

Always use one of these two ways to include files. This is required to include files even from the current directory. Some installations do not have the current directory in the PHP include path and require_once() without a proper path will result in a fatal PHP error.

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.

Taking again the example of file typo3/sysext/core/Classes/Cache/Backend/AbstractBackend.php, the PHP class declaration will look like:

class AbstractBackend implements \TYPO3\CMS\Core\Cache\Backend\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:

$controller = GeneralUtility::makeInstance(\Vendor\MyNamespace\MyExtension\Controller\AjaxController::class);
$controller->main();

This code must appear after the PHP class.