Noptin_Background_Sync::task( array $item )

	public function task( $item ) {

		// Item can either be a subscriber or a WordPress user.

		if( 'subscriber' == $item ) {

			// Fetch the next subscriber to sync.
			$subscriber = $this->get_unsynced_subscriber();

			// If all subscribers are synced, return false to stop the process.
			if ( empty( $subscriber ) ) {
				delete_option( 'noptin_subscribers_syncing' );
				return false;
			}

			// Else, sync the subscriber and move on to the next user on the list.
			sync_noptin_subscribers_to_users( $subscriber );
			return $item;

		} else if ( 'wp_user' == $item ) {

			// Fetch the next user to sync.
			$user = $this->get_unsynced_user();

			// If all users are synced, return false to stop the process.
			if ( empty( $user ) ) {
				delete_option( 'noptin_users_bg_sync' );
				return false;
			}

			// Else, sync the user and move on to the next user on the list.
			sync_users_to_noptin_subscribers( $user );
			return $item;

		}

	}