Since release 2.0, it is now possible to extend WordPress from the application root. Instead of relying on plugins in order to add functionality to your WordPress application, you can leverage "hookable" classes to do so.
When you write code inside a "hookable" class, you have access to all APIs defined by WordPress and your application packages. By default, "hookable" classes are loaded just before mu-plugins. It is also possible to run the class code at a specific WordPress action or filter hook and define its priority.
The Themosis framework is bundled with basic hookable classes. Those classes customize the default behavior of WordPress for you. The classes are stored inside the app/Hooks directory, and you can customize or extend them depending on your needs. Feel free to explore each one of them as each class contains self-explanatory comments to guide you. Just note that the Application hook class is the primary one and is responsible for loading some core features and the core Themosis framework assets.
Hookable classes are not automatically registered in the application lifecycle. Each time you create a new hookable class, you must register it inside the config/app.php file under its hooks property. If you explore the file, you'll see that the default classes are already registered.
In order to create a new hookable class, you may call the make:hook command:
php artisan make:hook MyHookThe command will generate a new class and store it inside the app/Hooks folder of your application:
<?php
namespace App\Hooks;
use Themosis\Hook\Hookable;
class MyHook extends Hookable
{
/**
* Extend WordPress.
*/
public function register()
{
// Execute your code...
}
}Write your code inside the register method. Once your code is added, you still need to register the hookable class within the hooks property of the config/app.php file like so:
'hooks' => [
App\Hooks\MyHook::class
]It is also possible to postpone the execution of a hookable class to a specific WordPress action hook. For example, you may want to run the code inside the register method only when the init action is triggered by WordPress.
To do so, simply define a $hook instance property on your class and set its value to one of the WordPress action hook:
<?php
namespace App\Hooks;
use Themosis\Hook\Hookable;
class HookOnInit extends Hookable
{
public $hook = 'init';
/**
* Extend WordPress.
*/
public function register()
{
// Code is executed on the "init" WordPress action only.
}
}It is also possible to define an execution priority by setting the $priority property like so:
<?php
namespace App\Hooks;
use Themosis\Hook\Hookable;
class HookOnInit extends Hookable
{
public $hook = 'init';
public $priority = 20;
/**
* Extend WordPress.
*/
public function register()
{
// Code is executed on the "init" WordPress action only.
}
}Hookable classes are only used at application root. There are used as an entry point into the WordPress APIs. If you develop custom plugins or work inside the theme, you don't need hookable classes because at that point, all WordPress APIs are already loaded.
If you need to execute some code at a specific action, simply use the Action class or the Filter class.
Because filters use the same API behind the scene, you can also perform some code on any WordPress filters. Define your filter logic inside the hookable class register() method, just like for an action. The difference here is that the register method is now receiving the filter parameters as arguments and that you need to return a value.
Here is an example of a filter on the the_title hook:
<?php
namespace App\Hooks;
use Themosis\Hook\Hookable;
class TitleFilter extends Hookable
{
public $hook = 'the_title';
public function register(string $title): string
{
return ucfirst($title);
}
}Then register your filter in the config/app.php file, just like an action hook class.
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