tinymce.php

<?php

namespace App;

if (class_exists('TinyMCE')) {
    return;
}

/**
 * TinyMCE
 */
class TinyMCE
{
    /**
     * Constructor
     */
    public function __construct()
    {
        if (is_admin()) {
            add_action('init', [$this, 'init']);
        }
    }

    /**
     * Initialize the TinyMCE object
     */
    public function init()
    {
        // Check if user has proper permissions & has rich editing enabled.
        if (!current_user_can('edit_posts') && !current_user_can('edit_pages') || get_user_option('rich_editing') !== 'true') {
            return;
        }

        // Setup the filters
        add_filter('mce_external_plugins', [$this, 'plugins']);
        add_filter('mce_buttons', [$this, 'buttons']);
    }

    /**
     * Add plugins to the TinyMCE / Visual Editor
     *
     * @param  array $plugin_array
     * @return array
     */
    public function plugins($plugin_array)
    {
        $plugin_array['app'] = \App\asset_path('scripts/tinymce.js');
        return $plugin_array;
    }

    /**
     * Add buttons to the TinyMCE / Visual Editor
     *
     * @param  array $buttons
     * @return array
     */
    public function buttons($buttons)
    {
        array_push($buttons, '', 'app');
        return $buttons;
    }
}

new TinyMCE();