This is the reference for Hooks which describes all the available hooks of the Contao core and their parameters. The examples in this reference implement Hooks using PHP Attributes and Invokable Services. These examples will work out of the box within a Contao 4.13 and 5.x installation under PHP 8 and higher. For lower Contao or PHP versions you need to use Service Annotations instead. If you need to implement a Hook for Contao 4.4, you still need to use the PHP array configuration. See here for more information on the topic of registering Hooks.