diff --git a/system/libs/forum.php b/system/libs/forum.php
index 648a9d99..4922a9c3 100644
--- a/system/libs/forum.php
+++ b/system/libs/forum.php
@@ -11,7 +11,7 @@
 defined('MYAAC') or die('Direct access not allowed!');
 
 $configForumTablePrefix = config('forum_table_prefix');
-if(!empty(trim($configForumTablePrefix))) {
+if(null !== $configForumTablePrefix && !empty(trim($configForumTablePrefix))) {
 	if(!in_array($configForumTablePrefix, array('myaac_', 'z_'))) {
 		throw new RuntimeException('Invalid value for forum_table_prefix in config.php. Can be only: "myaac_" or "z_".');
 	}
@@ -322,4 +322,4 @@ class Forum
 		return $hasAccess;
 	}
 }
-?>
\ No newline at end of file
+?>
diff --git a/system/libs/pot/OTS_Account.php b/system/libs/pot/OTS_Account.php
index beed47dd..e68f8034 100644
--- a/system/libs/pot/OTS_Account.php
+++ b/system/libs/pot/OTS_Account.php
@@ -31,7 +31,7 @@
  * @property-read int $access Access level.
  * @tutorial POT/Accounts.pkg
  */
-class OTS_Account extends OTS_Row_DAO implements IteratorAggregate, Countable
+class OTS_Account extends OTS_Row_DAO implements Countable
 {
 /**
  * Account data.
@@ -1033,7 +1033,7 @@ class OTS_Account extends OTS_Row_DAO implements IteratorAggregate, Countable
  * @throws PDOException On PDO operation error.
  * @return int Count of players.
  */
-    public function count()
+    public function count(): int
     {
         return $this->getPlayersList()->count();
     }
diff --git a/system/libs/pot/OTS_Base_List.php b/system/libs/pot/OTS_Base_List.php
index c3df55df..144d5ad7 100644
--- a/system/libs/pot/OTS_Base_List.php
+++ b/system/libs/pot/OTS_Base_List.php
@@ -36,7 +36,7 @@
  * @property-write int $offset Sets OFFSET clause.
  * @property-write OTS_SQLFilter $filter Sets filter for list SQL query.
  */
-abstract class OTS_Base_List implements IOTS_DAO, Iterator, Countable
+abstract class OTS_Base_List implements IOTS_DAO, Countable
 {
 /**
  * Database connection.
@@ -203,7 +203,7 @@ abstract class OTS_Base_List implements IOTS_DAO, Iterator, Countable
  *
  * @throws PDOException On PDO operation error.
  */
-    public function rewind()
+    public function rewind(): void
     {
         $this->rows = $this->db->query( $this->getSQL() )->fetchAll();
     }
@@ -211,7 +211,7 @@ abstract class OTS_Base_List implements IOTS_DAO, Iterator, Countable
 /**
  * Moves to next row.
  */
-    public function next()
+    public function next(): void
     {
         next($this->rows);
     }
@@ -231,7 +231,7 @@ abstract class OTS_Base_List implements IOTS_DAO, Iterator, Countable
  *
  * @return bool Does next row exist.
  */
-    public function valid()
+    public function valid(): bool
     {
         return key($this->rows) !== null;
     }
@@ -243,7 +243,7 @@ abstract class OTS_Base_List implements IOTS_DAO, Iterator, Countable
  * @return int Number of rows.
  * @throws PDOException On PDO operation error.
  */
-    public function count()
+    public function count(): int
     {
         return $this->db->query( $this->getSQL(true) )->fetchColumn();
     }
diff --git a/system/libs/pot/OTS_DB_PDOQuery_PHP71.php b/system/libs/pot/OTS_DB_PDOQuery_PHP71.php
index 3bb91a46..b6406b9a 100644
--- a/system/libs/pot/OTS_DB_PDOQuery_PHP71.php
+++ b/system/libs/pot/OTS_DB_PDOQuery_PHP71.php
@@ -5,7 +5,7 @@ trait OTS_DB_PDOQuery
 	/**
 	 * @return PDOStatement
 	 */
-	public function query(?string $query = null, ?int $fetchMode = null, mixed ...$fetchModeArgs)
+	public function query(?string $query = null, ?int $fetchMode = null, mixed ...$fetchModeArgs): PDOStatement
 	{
 		return $this->doQuery($query, $fetchMode, ...$fetchModeArgs);
 	}
diff --git a/system/libs/pot/OTS_Group.php b/system/libs/pot/OTS_Group.php
index 819d8b50..54b44f49 100644
--- a/system/libs/pot/OTS_Group.php
+++ b/system/libs/pot/OTS_Group.php
@@ -26,7 +26,7 @@
  * @property-read int $id Row ID.
  * @property-read OTS_Players_List $playersList List of members of this group.
  */
-class OTS_Group extends OTS_Row_DAO implements IteratorAggregate, Countable
+class OTS_Group extends OTS_Row_DAO implements Countable
 {
 /**
  * Group data.
@@ -552,7 +552,7 @@ class OTS_Group extends OTS_Row_DAO implements IteratorAggregate, Countable
  * @throws PDOException On PDO operation error.
  * @return int Count of players.
  */
-    public function count()
+    public function count(): int
     {
         return $this->getPlayersList()->count();
     }
diff --git a/system/libs/pot/OTS_Groups_List.php b/system/libs/pot/OTS_Groups_List.php
index 083615de..59440ecf 100644
--- a/system/libs/pot/OTS_Groups_List.php
+++ b/system/libs/pot/OTS_Groups_List.php
@@ -14,7 +14,7 @@
  * @package POT
  * @version 0.1.3
  */
-class OTS_Groups_List implements IteratorAggregate, Countable
+class OTS_Groups_List implements Countable
 {
 /**
  * Groups.
@@ -41,7 +41,7 @@ class OTS_Groups_List implements IteratorAggregate, Countable
 				$info['access'] = $group['name'];
 				$this->groups[$group['id']] = new OTS_Group($info);
 			}
-			
+
 			return;
 		}
 
@@ -50,7 +50,7 @@ class OTS_Groups_List implements IteratorAggregate, Countable
 			global $config;
 			$file = $config['data_path'] . 'XML/groups.xml';
 		}
-		
+
 		if(!@file_exists($file)) {
 			error('Error: Cannot load groups.xml. More info in system/logs/error.log file.');
 			log_append('error.log', '[OTS_Groups_List.php] Fatal error: Cannot load groups.xml (' . $file . '). It doesnt exist.');
@@ -99,7 +99,7 @@ class OTS_Groups_List implements IteratorAggregate, Countable
 				log_append('error.log', '[OTS_Groups_List.php] Fatal error: Cannot load groups.xml (' . $file . '). Error: ' . print_r(error_get_last(), true));
 				return;
 			}
-			
+
 			// loads groups
 			foreach($groups->getElementsByTagName('group') as $group)
 			{
@@ -157,7 +157,7 @@ class OTS_Groups_List implements IteratorAggregate, Countable
 			if($id > $group_id)
 				$group_id = $id;
 		}
-		
+
 		return $group_id;
 	}
 
@@ -210,7 +210,7 @@ class OTS_Groups_List implements IteratorAggregate, Countable
  * @since 0.1.5
  * @return int Amount of all groups.
  */
-    public function count()
+    public function count(): int
     {
         return count($this->groups);
     }
diff --git a/system/libs/pot/OTS_Guild.php b/system/libs/pot/OTS_Guild.php
index 27e3e102..4cafc0c3 100644
--- a/system/libs/pot/OTS_Guild.php
+++ b/system/libs/pot/OTS_Guild.php
@@ -30,7 +30,7 @@
  * @property-write IOTS_GuildAction $requestsDriver Membership requests handler.
  * @tutorial POT/Guilds.pkg
  */
-class OTS_Guild extends OTS_Row_DAO implements IteratorAggregate, Countable
+class OTS_Guild extends OTS_Row_DAO implements Countable
 {
 /**
  * Guild data.
@@ -723,7 +723,7 @@ class OTS_Guild extends OTS_Row_DAO implements IteratorAggregate, Countable
  * @throws PDOException On PDO operation error.
  * @return int Count of ranks.
  */
-    public function count()
+    public function count(): int
     {
         return $this->getGuildRanksList()->count();
     }
diff --git a/system/libs/pot/OTS_GuildRank.php b/system/libs/pot/OTS_GuildRank.php
index 24e1478c..4518eaa6 100644
--- a/system/libs/pot/OTS_GuildRank.php
+++ b/system/libs/pot/OTS_GuildRank.php
@@ -25,7 +25,7 @@
  * @property-read int $id Row ID.
  * @property-read OTS_Players_List $playersList List of members with this rank.
  */
-class OTS_GuildRank extends OTS_Row_DAO implements IteratorAggregate, Countable
+class OTS_GuildRank extends OTS_Row_DAO implements Countable
 {
 /**
  * Rank data.
@@ -410,7 +410,7 @@ class OTS_GuildRank extends OTS_Row_DAO implements IteratorAggregate, Countable
  * @throws PDOException On PDO operation error.
  * @return int Count of players.
  */
-    public function count()
+    public function count(): int
     {
         return $this->getPlayersList()->count();
     }