added admin function: add user

homepage/participo/lib/participoLib/participo.php

@@ -168,8 +168,9 @@ class participo
 	 * @retval true user with id $userId has attribute "isAdmin"
 	 * @retval false otherwise
 	 */
-	public static function isUserAdmin($userId)
+	public static function isUserAdmin($userId = null)
 	{
+		$userId = $userId ?? $_SESSION['user']['userId'];
 		return self::hasUserAttribute($userId, 'isAdmin');
 	}
 
@@ -550,8 +551,7 @@ function getHtmlSquareDate($date = null)
 		. '</div>';
 }
 
-/**
- * filter_var for a (db)id
+/** filter_var for a (db)id
  *
  * check for valid id; null is default; only values > 0 are excepted
  *