diff --git a/phpgwapi/inc/class.accounts_ads.inc.php b/phpgwapi/inc/class.accounts_ads.inc.php
index 89bd1212a8..9f399f74ff 100644
--- a/phpgwapi/inc/class.accounts_ads.inc.php
+++ b/phpgwapi/inc/class.accounts_ads.inc.php
@@ -139,12 +139,12 @@ class accounts_ads
 			if (empty($config['ads_host'])) throw new Exception("Required ADS host name(s) missing!");
 			if (empty($config['ads_domain'])) throw new Exception("Required ADS domain missing!");
 
-			$base_dn = array();
+			$base_dn_parts = array();
 			foreach(explode('.', $config['ads_domain']) as $dc)
 			{
-				$base_dn[] = 'DC='.$dc;
+				$base_dn_parts[] = 'DC='.$dc;
 			}
-			$base_dn = implode(',', $base_dn);
+			$base_dn = implode(',', $base_dn_parts);
 			$options = array(
 				'domain_controllers' => preg_split('/[ ,]+/', $config['ads_host']),
 				'base_dn' => $base_dn ? $base_dn : null,
@@ -170,10 +170,10 @@ class accounts_ads
 	 */
 	protected function get_sid($account_id=null)
 	{
-		static $domain_sid;
+		static $domain_sid = null;
 		if (!isset($domain_sid))
 		{
-			$domain_sid = egw_cache::getInstance(__CLASS__, 'ads_domain_sid');
+			$domain_sid = egw_cache::getCache($this->frontend->config['install_id'], __CLASS__, 'ads_domain_sid');
 			if ((!is_array($domain_sid) || !isset($domain_sid[$this->frontend->config['ads_domain']])) &&
 				($adldap = self::get_adldap($this->frontend->config)) &&
 				($sr = ldap_search($adldap->getLdapConnection(), $adldap->getBaseDn(), '(objectclass=domain)', array('objectsid'))) &&
@@ -181,7 +181,7 @@ class accounts_ads
 			{
 				$domain_sid = array();
 				$domain_sid[$this->frontend->config['ads_domain']] = $adldap->utilities()->getTextSID($entries[0]['objectsid'][0]);
-				egw_cache::setInstance(__CLASS__, 'ads_domain_sid', $domain_sid);
+				egw_cache::setCache($this->frontend->config['install_id'], __CLASS__, 'ads_domain_sid', $domain_sid);
 			}
 		}
 		$sid = $domain_sid[$this->frontend->config['ads_domain']];
@@ -231,6 +231,7 @@ class accounts_ads
 	{
 		$context = $this->ads_context(true);
 		$base = $this->adldap->getBaseDn();
+		$matches = null;
 		if (!preg_match('/^(.*),'.preg_quote($base, '/').'$/i', $context, $matches))
 		{
 			throw new egw_exception_wrong_userinput("Wrong or not configured ADS context '$context' (baseDN='$base')!");
@@ -556,7 +557,7 @@ class accounts_ads
 	 */
 	protected static function _when2ts($when)
 	{
-		static $utc;
+		static $utc=null;
 		if (!isset($utc)) $utc = new DateTimeZone('UTC');
 
 		list($when) = explode('.', $when);	// remove .0Z not understood by createFromFormat
@@ -1101,6 +1102,7 @@ class accounts_ads
 		{
 			foreach($this->filter(array($to_ldap[$which] => $name), $account_type) as $account_id => $account_lid)
 			{
+				unset($account_lid);
 				$ret = $account_id;
 				break;
 			}
@@ -1132,6 +1134,8 @@ class accounts_ads
 	 */
 	function update_lastlogin($_account_id, $ip)
 	{
+		unset($_account_id, $ip);	// not used, but required by function signature
+
 		return false;	// not longer supported
 	}
 
diff --git a/phpgwapi/inc/class.egw_cache.inc.php b/phpgwapi/inc/class.egw_cache.inc.php
index bed9f12441..26f72d0354 100644
--- a/phpgwapi/inc/class.egw_cache.inc.php
+++ b/phpgwapi/inc/class.egw_cache.inc.php
@@ -7,7 +7,7 @@
  * @package api
  * @subpackage cache
  * @author Ralf Becker <RalfBecker-AT-outdoor-training.de>
- * @copyright (c) 2009-13 by Ralf Becker <RalfBecker-AT-outdoor-training.de>
+ * @copyright (c) 2009-14 by Ralf Becker <RalfBecker-AT-outdoor-training.de>
  * @version $Id$
  */
 
@@ -45,6 +45,9 @@
  * resonable expiry times or think about an other means of clearing that particular item.
  * (Not clearing of tree-level cache is important, as regenerating it is an expensive
  * operation for a huge scale EGroupware hosting operation.)
+ *
+ * Apps needing to talk to multiple EGroupware instances (eg. Stylite Managementserver)
+ * can use install_id of instance as $level parameter to (set|get|unset)Cache method.
  */
 class egw_cache
 {
@@ -107,6 +110,7 @@ class egw_cache
 
 			case self::INSTANCE:
 			case self::TREE:
+			default:
 				if (!($provider = self::get_provider($level)))
 				{
 					return false;
@@ -147,6 +151,7 @@ class egw_cache
 
 			case self::INSTANCE:
 			case self::TREE:
+			default:
 				if (!($provider = self::get_provider($level)))
 				{
 					return null;
@@ -214,6 +219,7 @@ class egw_cache
 
 			case self::INSTANCE:
 			case self::TREE:
+			default:
 				if (!($provider = self::get_provider($level, false)))
 				{
 					return false;
@@ -445,7 +451,7 @@ class egw_cache
 	 *
 	 * The returned provider already has an opened connection
 	 *
-	 * @param string $level egw_cache::(TREE|INSTANCE)
+	 * @param string $level egw_cache::(TREE|INSTANCE) or install_id
 	 * @param boolean $log_not_found=true false do not log if no provider found, used eg. to supress error via unsetCache during installation
 	 * @return egw_cache_provider
 	 */
@@ -453,6 +459,8 @@ class egw_cache
 	{
 		static $providers = array();
 
+		if ($level != self::TREE) $level = self::INSTANCE;
+
 		if (!isset($providers[$level]))
 		{
 			$params = $GLOBALS['egw_info']['server']['cache_provider_'.strtolower($level)];
@@ -615,39 +623,43 @@ class egw_cache
 	/**
 	 * Get keys array from $level, $app and $location
 	 *
-	 * @param string $level egw_cache::(TREE|INSTANCE)
+	 * @param string $level egw_cache::(TREE|INSTANCE) or instance_id
 	 * @param string $app
 	 * @param string $location
 	 * @return array
 	 */
 	static public function keys($level,$app,$location)
 	{
-		static $bases = array();
+		static $tree_key = null;
 
-		if (!isset($bases[$level]) || $level == self::INSTANCE && $bases[$level] != self::$instance_key)
+		switch($level)
 		{
-			switch($level)
-			{
-				case self::TREE:
-					$bases[$level] = $level.'-'.str_replace(array(':','/','\\'),'-',EGW_SERVER_ROOT);
+			case self::TREE:
+				if (!isset($tree_key))
+				{
+					$tree_key = $level.'-'.str_replace(array(':','/','\\'),'-',EGW_SERVER_ROOT);
 					// add charset to key, if not utf-8 (as everything we store depends on charset!)
 					if (($charset = self::get_system_config('system_charset',false)) && $charset != 'utf-8')
 					{
-						$bases[$level] .= '-'.$charset;
+						$tree_key .= '-'.$charset;
 					}
-					break;
-				case self::INSTANCE:
-					if (!isset(self::$instance_key))
-					{
-						self::$instance_key = self::getTree(__CLASS__, self::get_system_config('install_id'));
-						//error_log(__METHOD__."('$level',...) instance_key read from tree-cache=".array2string(self::$instance_key));
-						if (!isset(self::$instance_key)) self::generate_instance_key();
-					}
-					$bases[$level] = self::$instance_key;
-					break;
-			}
+				}
+				$level_key = $tree_key;
+				break;
+			case self::INSTANCE:
+				if (!isset(self::$instance_key))
+				{
+					self::$instance_key = self::getTree(__CLASS__, self::get_system_config('install_id'));
+					//error_log(__METHOD__."('$level',...) instance_key read from tree-cache=".array2string(self::$instance_key));
+					if (!isset(self::$instance_key)) self::generate_instance_key();
+				}
+				$level_key = self::$instance_key;
+				break;
+			default:
+				$level_key = $level;
+				break;
 		}
-		return array($bases[$level],$app,$location);
+		return array($level_key, $app, $location);
 	}
 
 	/**