Error message

• Warning: preg_match(): Unknown modifier '2' in os_check() (line 252 of /var/www/custom/tools/tools.inc).
• Warning: preg_match(): Unknown modifier 'T' in os_check() (line 252 of /var/www/custom/tools/tools.inc).
• Warning: Undefined array key "profile" in include() (line 2 of /var/www/custom/include/realtime/chat_notifications.php).
• Warning: Trying to access array offset on value of type null in include() (line 2 of /var/www/custom/include/realtime/chat_notifications.php).