Some fixes:

- $gsid's default value cannot sadly be 0, it now must be null to allow some
  code work
- added some more type-hints
- documented a bit more

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);
 	}

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);
 

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;

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;