diff --git a/src/Content/ContactSelector.php b/src/Content/ContactSelector.php
index fd574889e6..db7ad80ca6 100644
--- a/src/Content/ContactSelector.php
+++ b/src/Content/ContactSelector.php
@@ -111,14 +111,16 @@ class ContactSelector
 	}
 
 	/**
+	 * Determines network name
+	 *
 	 * @param string $network  network of the contact
 	 * @param string $profile  optional, default empty
 	 * @param string $protocol (Optional) Protocol that is used for the transmission
-	 * @param int $gsid ??? (@TODO)
+	 * @param int $gsid Server id
 	 * @return string
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	public static function networkToName(string $network, string $profile = '', string $protocol = '', int $gsid = 0): string
+	public static function networkToName(string $network, string $profile = '', string $protocol = '', int $gsid = null): string
 	{
 		$nets = [
 			Protocol::DFRN      =>   DI::l10n()->t('DFRN'),
@@ -180,13 +182,15 @@ class ContactSelector
 	}
 
 	/**
+	 * Determines network's icon name
+	 *
 	 * @param string $network network
 	 * @param string $profile optional, default empty
-	 * @param int $gsid ??? (@TODO)
-	 * @return string
+	 * @param int $gsid Server id
+	 * @return string Name for network icon
 	 * @throws \Exception
 	 */
-	public static function networkToIcon(string $network, string $profile = "", int $gsid = 0): string
+	public static function networkToIcon(string $network, string $profile = "", int $gsid = null): string
 	{
 		$nets = [
 			Protocol::DFRN      =>   'friendica',
diff --git a/src/Database/DBA.php b/src/Database/DBA.php
index 2cafc4e0a6..d62edf6ce1 100644
--- a/src/Database/DBA.php
+++ b/src/Database/DBA.php
@@ -427,7 +427,7 @@ class DBA
 	 * @return boolean was the update successfull?
 	 * @throws \Exception
 	 */
-	public static function update($table, $fields, $condition, $old_fields = [], $params = [])
+	public static function update($table, array $fields, array $condition, $old_fields = [], array $params = [])
 	{
 		return DI::dba()->update($table, $fields, $condition, $old_fields, $params);
 	}
@@ -443,7 +443,7 @@ class DBA
 	 * @throws \Exception
 	 * @see   self::select
 	 */
-	public static function selectFirst($table, array $fields = [], array $condition = [], $params = [])
+	public static function selectFirst($table, array $fields = [], array $condition = [], array $params = [])
 	{
 		return DI::dba()->selectFirst($table, $fields, $condition, $params);
 	}
diff --git a/src/Model/Attach.php b/src/Model/Attach.php
index 9009126868..91970bfc62 100644
--- a/src/Model/Attach.php
+++ b/src/Model/Attach.php
@@ -102,7 +102,7 @@ class Attach
 	 * @return boolean
 	 * @throws \Exception
 	 */
-	public static function exists(array $conditions)
+	public static function exists(array $conditions): bool
 	{
 		return DBA::exists('attach', $conditions);
 	}
diff --git a/src/Model/Contact.php b/src/Model/Contact.php
index aea3faf3cd..949db50352 100644
--- a/src/Model/Contact.php
+++ b/src/Model/Contact.php
@@ -128,10 +128,10 @@ class Contact
 	 * @param array $fields    Array of selected fields, empty for all
 	 * @param array $condition Array of fields for condition
 	 * @param array $params    Array of several parameters
-	 * @return array
+	 * @return array|bool
 	 * @throws \Exception
 	 */
-	public static function selectFirst(array $fields = [], array $condition = [], array $params = []): array
+	public static function selectFirst(array $fields = [], array $condition = [], array $params = [])
 	{
 		$contact = DBA::selectFirst('contact', $fields, $condition, $params);
 
diff --git a/src/Model/GServer.php b/src/Model/GServer.php
index c0e4899923..ff22730e4e 100644
--- a/src/Model/GServer.php
+++ b/src/Model/GServer.php
@@ -2054,7 +2054,7 @@ class GServer
 	 * @return int
 	 * @throws Exception
 	 */
-	public static function getProtocol(int $gsid)
+	public static function getProtocol(int $gsid): int
 	{
 		if (empty($gsid)) {
 			return null;
diff --git a/src/Model/Photo.php b/src/Model/Photo.php
index d9e6f7cade..fd387e56e8 100644
--- a/src/Model/Photo.php
+++ b/src/Model/Photo.php
@@ -110,7 +110,7 @@ class Photo
 	 * @throws \Exception
 	 * @see   \Friendica\Database\DBA::select
 	 */
-	public static function getPhotosForUser($uid, $resourceid, array $conditions = [], array $params = [])
+	public static function getPhotosForUser(int $uid, string $resourceid, array $conditions = [], array $params = [])
 	{
 		$conditions["resource-id"] = $resourceid;
 		$conditions["uid"] = $uid;
diff --git a/src/Network/Probe.php b/src/Network/Probe.php
index c5ecf96ed3..d8a1593313 100644
--- a/src/Network/Probe.php
+++ b/src/Network/Probe.php
@@ -1445,7 +1445,7 @@ class Probe
 	 * @return array|bool OStatus data or "false" on error or "true" on short mode
 	 * @throws HTTPException\InternalServerErrorException
 	 */
-	private static function ostatus($webfinger, $short = false)
+	private static function ostatus(array $webfinger, bool $short = false)
 	{
 		$data = [];
 
diff --git a/src/Util/Strings.php b/src/Util/Strings.php
index 8666d30c18..d2555132a0 100644
--- a/src/Util/Strings.php
+++ b/src/Util/Strings.php
@@ -165,7 +165,7 @@ class Strings
 	 * @return string Formatted network name
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	public static function formatNetworkName($network, $url = '')
+	public static function formatNetworkName(string $network, string $url = ''): string
 	{
 		if ($network != '') {
 			if ($url != '') {
@@ -176,6 +176,8 @@ class Strings
 
 			return $network_name;
 		}
+
+		return '';
 	}
 
 	/**
@@ -187,7 +189,7 @@ class Strings
 	 *
 	 * @return string		Transformed string.
 	 */
-	public static function deindent($text, $chr = "[\t ]", $count = NULL)
+	public static function deindent(string $text, string $chr = "[\t ]", int $count = null)
 	{
 		$lines = explode("\n", $text);