diff --git a/config.php b/config.php
index 7c945423..5b00533a 100644
--- a/config.php
+++ b/config.php
@@ -24,11 +24,11 @@ $GLOBALS['CONFIG']['PREVIEW_DOMAIN'] = 'xlocalhost';
  * Protokollfreie URLs (welche, die mit // beginnen), werden automatisch mit dem korrekten Protokoll ergänzt.
  * In diesem Fall wird auch ein SSL-Umschalt-Button im Header angezeigt
  */
-if(@$_SERVER['SERVER_NAME'] == 'localhost' || @$_SERVER['SERVER_NAME'] == '0.0.0.0')
+if(isset($_SERVER['SERVER_NAME']) && ($_SERVER['SERVER_NAME'] == 'localhost' || $_SERVER['SERVER_NAME'] == '0.0.0.0'))
 {
 	// keine Konfiguration -> BASEURL wird automatisch erraten
 }
-else if(@$_SERVER['SERVER_NAME'] == 'streaming.test.c3voc.de')
+else if(isset($_SERVER['SERVER_NAME']) && ($_SERVER['SERVER_NAME'] == 'streaming.test.c3voc.de'))
 {
 	$GLOBALS['CONFIG']['BASEURL'] = '//streaming.test.c3voc.de/';
 }
@@ -104,7 +104,7 @@ $GLOBALS['CONFIG']['FEEDBACK'] = array(
 /**
  * Konfiguration der Room-Defaults
  *
- * Falls in der Raum-Konfiguration innerhalb der Konferenz für diese Keys nichts definiert ist, 
+ * Falls in der Raum-Konfiguration innerhalb der Konferenz für diese Keys nichts definiert ist,
  * fällt das System auf diese Werte zurück.
  */
 
diff --git a/index.php b/index.php
index 2d5a5fd8..a53b9e0a 100644
--- a/index.php
+++ b/index.php
@@ -52,11 +52,11 @@ if(isset($argv) && isset($argv[1]))
 try {
 	if(isset($_GET['htaccess']))
 	{
-		$route = @$_GET['route'];
+		$route = isset($_GET['route']) ? $_GET['route'] : "";
 	}
 	elseif(isset($_SERVER["REQUEST_URI"]))
 	{
-		$route = ltrim(@$_SERVER["REQUEST_URI"], '/');
+		$route = ltrim($_SERVER["REQUEST_URI"], '/');
 
 		// serve static
 		if($route != '' && file_exists($_SERVER["DOCUMENT_ROOT"].'/'.$route))
@@ -87,11 +87,12 @@ try {
 		'conference' => new GenericConference(),
 	));
 
-	if(isset($GLOBALS['CONFIG']['BASEURL']) && startswith('//', @$GLOBALS['CONFIG']['BASEURL']))
+	if(isset($GLOBALS['CONFIG']['BASEURL']) && startswith('//', $GLOBALS['CONFIG']['BASEURL']))
 	{
+		$mandator = isset($GLOBALS['MANDATOR']) ? $GLOBALS['MANDATOR'] : "";
 		$tpl->set(array(
-			'httpsurl' => forceslash(forceslash('https:'.$GLOBALS['CONFIG']['BASEURL']).@$GLOBALS['MANDATOR']).forceslash($route).url_params(),
-			'httpurl' =>  forceslash(forceslash('http:'. $GLOBALS['CONFIG']['BASEURL']).@$GLOBALS['MANDATOR']).forceslash($route).url_params(),
+			'httpsurl' => forceslash(forceslash('https:'.$GLOBALS['CONFIG']['BASEURL']).$mandator).forceslash($route).url_params(),
+			'httpurl' =>  forceslash(forceslash('http:'. $GLOBALS['CONFIG']['BASEURL']).$mandator).forceslash($route).url_params(),
 		));
 	}
 
diff --git a/lib/helper.php b/lib/helper.php
index 43c87481..b1c86672 100644
--- a/lib/helper.php
+++ b/lib/helper.php
@@ -244,8 +244,20 @@ function query_data($operation, $query, $variables = [], $assoc = false, $cache
 	if (is_null($r)) {
 		throw new NotFoundException();
 	}
-
+	
 	// TODO: add error handling?
 	// TODO: should we return the cached value, when we did not get an answer? 
-	return $assoc ? @$r['data'] : @$r->data;
+	if ($assoc) {
+		if (isset($r['data'])) {
+			return $r['data'];
+		} else {
+			throw new NotFoundException();
+		}
+	} else {
+		if (isset($r->data)) {
+			return $r->data;
+		} else {
+			throw new NotFoundException();
+		}
+	}
 }
\ No newline at end of file
diff --git a/model/Conference.php b/model/Conference.php
index 971bccc4..41096408 100644
--- a/model/Conference.php
+++ b/model/Conference.php
@@ -20,7 +20,7 @@ class Conference extends ModelBase
 	}
 
 	public function isPreviewEnabled() {
-		if(@$GLOBALS['forceopen'])
+		if(isset($GLOBALS['forceopen']) && $GLOBALS['forceopen'])
 			return true;
 
 		if($this->has('PREVIEW_DOMAIN') && ($this->get('PREVIEW_DOMAIN') == $_SERVER['SERVER_NAME']))
diff --git a/model/ConferenceJson.php b/model/ConferenceJson.php
index 89678f6f..409207f9 100644
--- a/model/ConferenceJson.php
+++ b/model/ConferenceJson.php
@@ -12,26 +12,32 @@ class ConferenceJson extends Conference
 		$c = $json->conference;
 		$this->start = DateTime::createFromFormat(DateTimeInterface::ISO8601, $c->start);
 		$this->end   = DateTime::createFromFormat(DateTimeInterface::ISO8601, $c->end);
-		$this->html  = @$c->streamingConfig->html ?: [];
+		$this->html  = isset($c->streamingConfig->html) ? $c->streamingConfig->html : [];
 
 		$this->rooms = [];
-		$rooms = (is_array(@$c->rooms) ? $c->rooms : @$c->rooms->nodes) ?: [];
+		if (isset($c->rooms)) {
+			if (is_array($c->rooms)) {
+				$rooms = $c->rooms;
+			} else {
+				$rooms = isset($c->rooms->nodes) ? $c->rooms->nodes : [];
+			}
+		}
 		foreach($rooms as $r) {
 			if (!$r) {
 				continue;
 			}
 			$this->rooms[$r->slug] = array_merge(
 				['stream' => $r->streamId],
-				get_object_vars($r), 
-				@get_object_vars($r->streamingConfig) ?: [], 
-				@get_object_vars($r->streamingConfig->chat) ?: []
+				get_object_vars($r),
+				(isset($r->streamingConfig) ? get_object_vars($r->streamingConfig) : []),
+				(isset($r->streamingConfig->chat) ? get_object_vars($r->streamingConfig->chat) : [])
 			);
 		}
 
 		$groups = [];
 		if ( isset($c->streamingConfig->overviewPage->sections) ) {
-			foreach(@$c->streamingConfig->overviewPage->sections as $s) {
-				$groups[@$s->title] = array_map(
+			foreach($c->streamingConfig->overviewPage->sections as $s) {
+				$groups[$s->title] = array_map(
 					function($r) { return $r->slug; }, 
 					@$s->items ?: @$s->rooms ?: []
 				);
@@ -44,15 +50,15 @@ class ConferenceJson extends Conference
 		$acronym = $mandator ?: $c->acronym;
 
 		parent::__construct(array_merge(
-			@get_object_vars($c->streamingConfig) ?: [], 
-			@get_object_vars($c->streamingConfig->features) ?: [],
-			@get_object_vars($c->streamingConfig->features->chat) ?: [],
+			isset($c->streamingConfig) ? get_object_vars($c->streamingConfig) : [],
+			isset($c->streamingConfig->features) ? get_object_vars($c->streamingConfig->features) : [],
+			isset($c->streamingConfig->features->chat) ? get_object_vars($c->streamingConfig->features->chat) : [],
 			[
 				'conference' => [
 					'title' 		=> $c->title,
 					'author' 		=> $c->organizer,
 					'description' 	=> $c->description,
-					'keywords'		=> @implode(', ', $c->keywords),
+					'keywords'		=> is_array($c->keywords) ? implode(', ', $c->keywords) : "",
 					// future TODO: change structure
 					"relive_json"	=> @$c->streamingConfig->features->relive !== false ? "https://cdn.c3voc.de/relive/".$acronym."/index.json" : null,
 					"releases"		=> @$c->streamingConfig->features->releases !== false ? "https://media.ccc.de/c/".$acronym : null
@@ -140,21 +146,21 @@ class ConferenceJson extends Conference
 		return !empty($this->html->banner);
 	}
 	public function getBannerHtml() {
-		return @$this->html->banner;
+		return isset($this->html->banner) ? $this->html->banner : "";
 	}
 
 	public function hasFooterHtml() {
 		return !empty($this->html->footer);
 	}
 	public function getFooterHtml() {
-		return @$this->html->footer;
+		return isset($this->html->footer) ? $this->html->footer : "";
 	}
 
 	public function hasNotStartedHtml() {
 		return !empty($this->html->not_started);
 	}
 	public function getNotStartedHtml() {
-		return @$this->html->not_started;
+		return isset($this->html->not_started) ? $this->html->not_started : "";
 	}
 
 }
diff --git a/model/Conferences.php b/model/Conferences.php
index 911b49cc..f2d06a00 100644
--- a/model/Conferences.php
+++ b/model/Conferences.php
@@ -65,7 +65,8 @@ class Conferences
 	}
 
 	public static function getLastConference() {
-		return @Conferences::getFinishedConferencesSorted()[0];
+		$conferences = Conferences::getFinishedConferencesSorted();
+		return isset($conferences[0]) ? $conferences[0] : null;
 	}
 
 	public static function exists($mandator) {
@@ -133,7 +134,7 @@ class Conferences
 		}
 
 		// config option for dynamic lookup feature defined below
-		if (!@$GLOBALS['CONFIG']['DYNAMIC_LOOKUP']) {
+		if (isset($GLOBALS['CONFIG']['DYNAMIC_LOOKUP']) && !$GLOBALS['CONFIG']['DYNAMIC_LOOKUP']) {
 			throw new NotFoundException();;
 		}
 
diff --git a/model/Feedback.php b/model/Feedback.php
index 7b603c94..fc154399 100644
--- a/model/Feedback.php
+++ b/model/Feedback.php
@@ -10,9 +10,10 @@ class Feedback
 	}
 
 	private function get($key) {
+		$global_feedback_elem = isset($GLOBALS['CONFIG']['FEEDBACK'][$key]) ? $GLOBALS['CONFIG']['FEEDBACK'][$key] : "";
 		return $this->conference->has(['FEEDBACK', $key])
 			? $this->conference->get(['FEEDBACK', $key])
-			: @$GLOBALS['CONFIG']['FEEDBACK'][$key];
+			: $global_feedback_elem;
 	}
 
 	public function getConference() {
diff --git a/model/Schedule.php b/model/Schedule.php
index a95e2402..5b3465bc 100644
--- a/model/Schedule.php
+++ b/model/Schedule.php
@@ -364,7 +364,15 @@ class Schedule
 			$this->mapping = array();
 			foreach($this->getConference()->get('ROOMS') as $slug => $room)
 			{
-				$key = @$room['name'] ?: @$room['SCHEDULE_NAME'] ?: @$room['DISPLAY'] ?: $slug; 
+				// json has 'name', config.php has 'SCHEDULE_NAME' and 'DISPLAY'
+				$key = $slug;
+				if (isset($room['name'])) {
+					$key = $room['name'];
+				} elseif ($room['SCHEDULE_NAME']) {
+					$key = $room['SCHEDULE_NAME'];
+				} elseif ($room['DISPLAY']) {
+					$key = $room['DISPLAY'];
+				}
 				$this->mapping[$key] = $slug;
 			}
 		}
diff --git a/view/allclosed.php b/view/allclosed.php
index 535e6e3a..a3f87fde 100644
--- a/view/allclosed.php
+++ b/view/allclosed.php
@@ -6,7 +6,7 @@ echo $tpl->render(array(
 	'page' => 'allclosed',
 	'title' => 'See you soon … somewhere else!',
 
-	'next' => @$events[0],
+	'next' => isset($events[0]) ? $events[0] : null,
 	'events' => $events,
 	'last' => Conferences::getLastConference(),
 ));
diff --git a/view/closed.php b/view/closed.php
index 32a132e1..4ca0c449 100644
--- a/view/closed.php
+++ b/view/closed.php
@@ -6,6 +6,6 @@ echo $tpl->render(array(
 	'page' => 'closed',
 	'title' => 'See you soon … somewhere else!',
 
-	'next' => @$events[0],
+	'next' => isset($events[0]) ? $events[0] : null,
 	'events' => $events,
 ));
diff --git a/view/embed.php b/view/embed.php
index 2071c3a1..c0e38f4d 100644
--- a/view/embed.php
+++ b/view/embed.php
@@ -28,5 +28,5 @@ echo $tpl->render(array(
 	'room' => $room,
 	'stream' => $stream,
 
-	'autoplay' => @$_GET['autoplay'],
+	'autoplay' => isset($_GET['autoplay']) ? $_GET['autoplay'] : false,
 ));
diff --git a/view/multiview.php b/view/multiview.php
index 68259116..91011312 100644
--- a/view/multiview.php
+++ b/view/multiview.php
@@ -5,5 +5,5 @@ echo $tpl->render(array(
 	'title' => 'Stream-Übersicht',
 
 	'rooms' => $conference->getRooms(),
-	'selection' => @$_GET['selection'],
+	'selection' => isset($_GET['selection']) ? $_GET['selection'] : "",
 ));