But if I replace that with the code you said, will not prevent the admin hack? 
Also I did it but still saying MULTI in the logs and I retested by sending accs money. 
However it's because I followed a security tutorial on MWG. 
Although in my authenticate.php I have this: 
  
$_SESSION['userid']=$mem['userid']; 
$IP = ($_SERVER['HTTP_X_FORWARDED_FOR']) 
 ? $_SERVER['HTTP_X_FORWARDED_FOR'] 
 : $_SERVER['REMOTE_ADDR'];