WordPress Admin Notice Helper Class

admin-notice-class.php

<?php

/**
 * Helper to work with Wordpress admin notices
 *
 * @example
 * Notice::success('All is good!');
 *
 * @example
 * Notice::warning('Do something please.', true);
 *
 * @example
 * Notice::info('Are you ok?', function ($id) {
 *     return 'jQuery(document).on("click", "#' . $id . ' .notice-dismiss", function () {
 *         // do something on dismiss...
 *     });';
 * });
 */
class Notice {
    private static $_instance = null;
    public $notices = [];
    public $scripts = [];

    public function __construct()
    {
        // @see https://codex.wordpress.org/Plugin_API/Action_Reference/admin_notices
        add_action('admin_notices', [&$this, 'display']);
        // @see https://codex.wordpress.org/Plugin_API/Action_Reference/admin_footer
        add_action('admin_footer', [&$this, 'scripts']);
    }

    public function display()
    {
        echo implode(' ', $this->notices);
    }

    public function scripts()
    {
        echo implode(' ', $this->scripts);
    }

    public static function getInstance()
    {
        if (is_null(self::$_instance)) {
            self::$_instance = new Notice();
        }

        return self::$_instance;
    }

    /**
     * @param $message - Message to display
     * @param string $type - Type of the notice (default: '')
     * @param mixed $isDismissible - If true, allow to dismiss. Could be a function that return javascript.
     */
    public static function add($message, $type = '', $isDismissible = null)
    {
        $instance = self::getInstance();

        $identifier = 'notice-' . (count($instance->notices) + 1);
        $notice = '<div class="notice' . (empty($type) ? '' : ' notice-' . $type) . (is_null($isDismissible) ? '' : ' is-dismissible') . '" id="' . $identifier . '" style="padding: 15px;">' . $message . '</div>';

        if (is_callable($isDismissible)) {
            $instance->scripts[] = '<script>' . $isDismissible($identifier) . '</script>';
        }

        $instance->notices[] = $notice;
    }

    /**
     * @param string $message - Message to display
     * @param mixed $isDismissible - If true, allow to dismiss. Could be a function that return javascript.
     */
    public static function info($message, $isDismissible = null)
    {
        self::add($message, 'info', $isDismissible);
    }

    /**
     * @param string $message - Message to display
     * @param mixed $isDismissible - If true, allow to dismiss. Could be a function that return javascript.
     */
    public static function error($message, $isDismissible = null)
    {
        self::add($message, 'error', $isDismissible);
    }

    /**
     * @param string $message - Message to display
     * @param mixed $isDismissible - If true, allow to dismiss. Could be a function that return javascript.
     */
    public static function success($message, $isDismissible = null)
    {
        self::add($message, 'success', $isDismissible);
    }

    /**
     * @param string $message - Message to display
     * @param mixed $isDismissible - If true, allow to dismiss. Could be a function that return javascript.
     */
    public static function warning($message, $isDismissible = null)
    {
        self::add($message, 'warning', $isDismissible);
    }
}