Automattic/php-push

<?php
declare( strict_types = 1 );

class APNSPushType {
    public const ALERT        = 'alert';
    public const BACKGROUND   = 'background';
    public const MDM          = 'mdm';
    public const VOIP         = 'voip';
    public const FILEPROVIDER = 'fileprovider';

    public static function is_valid( string $key ): bool {
        return in_array(
            $key,
            [
                self::ALERT,
                self::BACKGROUND,
                self::MDM,
                self::VOIP,
                self::FILEPROVIDER,
            ],
            true
        );
    }
}