WordPress admin page system

AbstractRenderedAdminPage.php

<?php

/**
 * A WordPress admin page rendered using a PHP template.
 */
abstract class MyPlugin_AbstractRenderedAdminPage implements MyPlugin_AdminPageInterface
{
    /**
     * Path to the admin page's templates.
     *
     * @var string
     */
    protected $template_path;
 
    /**
     * Constructor.
     *
     * @param string $template_path
     */
    public function __construct($template_path)
    {
        $this->template_path = rtrim($template_path, '/');
    }
 
    /**
     * Render the admin page.
     */
    public function render_page()
    {
        $this->render_template('page');
    }
 
    /**
     * Renders the given template if it's readable.
     *
     * @param string $template
     */
    protected function render_template($template)
    {
        $template_path = $this->template_path . '/' . $template . '.php';
 
        if (!is_readable($template_path)) {
            return;
        }
 
        include $template_path;
    }
}

AdminPageInterface.php

<?php

/**
 * A WordPress admin page.
 */
interface MyPlugin_AdminPageInterface
{
    /**
     * Get the capability required to view the admin page.
     *
     * @return string
     */
    public function get_capability();

    /**
     * Get the title of the admin page in the WordPress admin menu.
     *
     * @return string
     */
    public function get_menu_title();

    /**
     * Get the title of the admin page.
     *
     * @return string
     */
    public function get_page_title();

    /**
     * Get the parent slug of the admin page.
     *
     * @return string
     */
    public function get_parent_slug();

    /**
     * Get the slug used by the admin page.
     *
     * @return string
     */
    public function get_slug();

    /**
     * Renders the admin page.
     */
    public function render_page();
}

AdminPagesSubscriber.php

<?php

/**
 * Subscriber that registers the plugin's admin pages with WordPress.
 */
class MyPlugin_AdminPagesSubscriber implements MyPlugin_SubscriberInterface
{
    /**
     * The admin pages that the subscriber manages.
     *
     * @var MyPlugin_AdminPageInterface[]
     */
    private $admin_pages;
 
    /**
     * Constructor.
     *
     * @param MyPlugin_AdminPageInterface[] $admin_pages
     */
    public function __construct(array $admin_pages)
    {
        $this->admin_pages = array();
 
        foreach ($admin_pages as $admin_page) {
            $this->add_admin_page($admin_page);
        }
    }
  
    /**
     * Returns an array of events that this subscriber wants to listen to.
     *
     * The array key is the event name. The value can be:
     *
     *  * The method name
     *  * An array with the method name and priority
     *  * An array with the method name, priority and number of accepted arguments
     *
     * For instance:
     *
     *  * array('event_name' => 'method_name')
     *  * array('event_name' => array('method_name', $priority))
     *  * array('event_name' => array('method_name', $priority, $accepted_args))
     *
     * @return array
     */
    public static function get_subscribed_events()
    {
        return array(
            'admin_init' => 'configure_admin_pages',
            'admin_menu' => 'add_admin_pages',
        );
    }
 
    /**
     * Adds the plugin's admin pages to the WordPress admin.
     */
    public function add_admin_pages()
    {
        foreach ($this->admin_pages as $admin_page) {
            add_submenu_page(
                $admin_page->get_parent_slug(),
                $admin_page->get_page_title(),
                $admin_page->get_menu_title(),
                $admin_page->get_capability(),
                $admin_page->get_slug(),
                array($admin_page, 'render_page')
            );
        }
    }
 
    /**
     * Configure the plugin's admin pages using the Settings API.
     */
    public function configure_admin_pages()
    {
        foreach ($this->admin_pages as $admin_page) {
            if ($admin_page instanceof MyPlugin_ConfigurableAdminPageInterface) {
                $admin_page->configure();
            }
        }
    }
  
    /**
     * Add a new admin page to the subscriber.
     *
     * @param MyPlugin_AdminPageInterface $admin_page
     */
    private function add_admin_page(MyPlugin_AdminPageInterface $admin_page)
    {
        $this->admin_pages[] = $admin_page;
    }
}

ConfigurableAdminPageInterface.php

<?php

/**
 * A WordPress admin page configured using the settings API.
 */
interface MyPlugin_ConfigurableAdminPageInterface extends MyPlugin_AdminPageInterface
{
    /**
     * Configure the admin page using the Settings API.
     */
    public function configure();
}

functions.php

<?php

function myplugin_get_admin_pages() {
    return array(
        // Put admin page objects here
    );
}

function myplugin_add_admin_pages() {
    $admin_pages = myplugin_get_admin_pages();
 
    foreach ($admin_pages as $admin_page) {
        add_submenu_page(
            $admin_page->get_parent_slug(),
            $admin_page->get_page_title(),
            $admin_page->get_menu_title(),
            $admin_page->get_capability(),
            $admin_page->get_slug(),
            array($admin_page, 'render_page')
        );
    }
}
add_action('admin_menu', 'myplugin_add_admin_pages');

function myplugin_configure_admin_pages() {
    $admin_pages =  myplugin_get_admin_pages();
 
    foreach ($admin_pages as $admin_page) {
        if ($admin_page instanceof MyPlugin_ConfigurableAdminPageInterface) {
            $admin_page->configure();
        }
    }
}
add_action('admin_init', 'myplugin_configure_admin_pages');