diff --git a/server/lib/classes/backup.inc.php b/server/lib/classes/backup.inc.php
index 07ecdf11d0349d670e333a5879367e26f2e78f44..77011e61cb80ab1ffecbf9df65d765d7741cd39a 100644
--- a/server/lib/classes/backup.inc.php
+++ b/server/lib/classes/backup.inc.php
@@ -1497,9 +1497,9 @@ class backup
         foreach ($backup_excludes as $ex) {
             # pass through escapeshellarg if not already done
             if ( preg_match( "/^'.+'$/", $ex ) ) {
-                $excludes .= "${arg}${pre}${ex}${post} ";
+                $excludes .= "{$arg}{$pre}{$ex}{$post} ";
             } else {
-                $excludes .= "${arg}" . escapeshellarg("${pre}${ex}${post}") . " ";
+                $excludes .= "{$arg}" . escapeshellarg("{$pre}{$ex}{$post}") . " ";
             }
         }
 
@@ -1870,8 +1870,8 @@ class backup
             //* Remove old backups
             self::backups_garbage_collection($server_id, 'mysql', $domain_id);
             $prefix_list = array(
-                        "db_${db_name}_",
-                        "manual-db_${db_name}_",
+                        "db_{$db_name}_",
+                        "manual-db_{$db_name}_",
                     );
             self::clearBackups($server_id, $domain_id, intval($rec['backup_copies']), $db_backup_dir, $prefix_list);
         }
diff --git a/server/lib/classes/cron.d/100-monitor_clamav_log.inc.php b/server/lib/classes/cron.d/100-monitor_clamav_log.inc.php
index f2120539b47c95a49a661f9c4183f03f8a01c158..87e59376567e99948d71054c7ad80a643d37c11c 100644
--- a/server/lib/classes/cron.d/100-monitor_clamav_log.inc.php
+++ b/server/lib/classes/cron.d/100-monitor_clamav_log.inc.php
@@ -94,6 +94,7 @@ class cronjob_monitor_clamav_log extends cronjob {
 
 		/* Get the data of the log */
 		$data = $this->_tools->_getLogData($type);
+		if ($data == null) $data = "\n";
 
 		/* Get the data from the LAST log-Entry.
 		 * if there can be found:
diff --git a/server/lib/classes/cron.d/100-monitor_mail_queue.inc.php b/server/lib/classes/cron.d/100-monitor_mail_queue.inc.php
index f39dd00a6eea4c917980ba0a4f2cc7ae5e99f854..1463d7f1e2367db3bcc31cf9a30e75276473da30 100644
--- a/server/lib/classes/cron.d/100-monitor_mail_queue.inc.php
+++ b/server/lib/classes/cron.d/100-monitor_mail_queue.inc.php
@@ -82,6 +82,7 @@ class cronjob_monitor_mail_queue extends cronjob {
 
 		/* Get the data from the mailq */
 		$data['output'] = shell_exec('mailq');
+		if ($data['output'] == null) $data['output'] = "";
 
 		/*
 		 *  The last line has more informations
diff --git a/server/lib/classes/cron.d/100-monitor_system_update.inc.php b/server/lib/classes/cron.d/100-monitor_system_update.inc.php
index cab5f68edb0f7230d955da4c228f442a983db489..2bec71d8d248b152c59c872abe5ba8efd58d4744 100644
--- a/server/lib/classes/cron.d/100-monitor_system_update.inc.php
+++ b/server/lib/classes/cron.d/100-monitor_system_update.inc.php
@@ -216,7 +216,7 @@ class cronjob_monitor_system_update extends cronjob {
 
 		//* Ensure that output is encoded so that it does not break the serialize
 		//$res['data']['output'] = htmlentities($res['data']['output']);
-		$res['data']['output'] = htmlentities($res['data']['output'], ENT_QUOTES, 'UTF-8');
+		$res['data']['output'] = $res['data']['output'] ? htmlentities($res['data']['output'], ENT_QUOTES, 'UTF-8') : null;
 
 		/*
 		 * Insert the data into the database
diff --git a/server/lib/classes/db_mysql.inc.php b/server/lib/classes/db_mysql.inc.php
index f2299de343633c901842d3aa8ce1e5a9be52591d..44355ebfbb43cea57d6a62162299d61666b0bd28 100644
--- a/server/lib/classes/db_mysql.inc.php
+++ b/server/lib/classes/db_mysql.inc.php
@@ -668,7 +668,7 @@ class db
 			$clientdb_user     = ($conf['db_user']) ? $conf['db_user'] : NULL;
 			$clientdb_password = ($conf['db_password']) ? $conf['db_password'] : NULL;
 			$clientdb_port     = ((int)$conf['db_port']) ? (int)$conf['db_port'] : NULL;
-			$clientdb_flags    = ($conf['db_flags'] !== NULL) ? $conf['db_flags'] : NULL;
+			$clientdb_flags    = (isset($conf['db_flags']) && $conf['db_flags'] !== NULL) ? $conf['db_flags'] : NULL;
 
 			require_once 'lib/mysql_clientdb.conf';