Hook.php

<?php

namespace AC\Deprecated;

abstract class Hook
{

    /** @var string */
    private $name;

    /** @var string */
    private $version;

    /** @var string */
    private $slug;

    public function __construct($name, $version, $slug = null)
    {
        $this->name = $name;
        $this->version = $version;
        $this->slug = $slug;
    }

    /**
     * @return string
     */
    public function get_name()
    {
        return $this->name;
    }

    /**
     * @return string
     */
    public function get_version()
    {
        return $this->version;
    }

    /**
     * @return string
     */
    public function get_slug()
    {
        return $this->slug;
    }

    /**
     * @return bool
     */
    abstract public function has_hook();

    public function get_callbacks(): ?array
    {
        global $wp_filter;

        if ( ! isset($wp_filter[$this->name])) {
            return null;
        }

        if (empty($wp_filter[$this->name]->callbacks)) {
            return null;
        }

        $callbacks = [];

        foreach ($wp_filter[$this->name]->callbacks as $callback) {
            foreach ($callback as $cb) {
                // Function
                if (is_scalar($cb['function'])) {
                    $callbacks[] = $cb['function'];
                }

                // Method
                if (is_array($cb['function'])) {
                    $callbacks[] = get_class($cb['function'][0]) . '::' . $cb['function'][1];
                }
            }
        }

        if ( ! $callbacks) {
            return null;
        }

        return $callbacks;
    }

}