nextcloud/apps/contacts/ajax/activation.php

<?php
/**
 * Copyright (c) 2011 Thomas Tanghus <thomas@tanghus.net>
 * Copyright (c) 2011 Bart Visscher <bartv@thisnet.nl>
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */

require_once ("../../../lib/base.php");
OC_JSON::checkLoggedIn();
OC_JSON::checkAppEnabled('contacts');
$bookid = $_POST['bookid'];
OC_Contacts_Addressbook::setActive($bookid, $_POST['active']);
$book = OC_Contacts_App::getAddressbook($bookid);

/* is there an OC_JSON::error() ? */
OC_JSON::success(array(
	'active' => OC_Contacts_Addressbook::isActive($bookid),
	'bookid' => $bookid,
	'book'   => $book,
));