nechce mi fungovat script

<?php
ob_start();              
  if(isset($_POST['aktualne_heslo'])){
       
    $password=md5($_POST['aktualne_heslo']);
    $password1=$_POST['nove_heslo'];
    $password2=$_POST['nove_heslo1'];
    
    if($password=="" or $password1==""){
     
      $backlink="index.php?page=nastavenia&chyba=zmena_hesla";
    
    }else{ 
               
      require "../../db.php";  
         
      $vyber=mysql_query("SELECT * FROM users WHERE user_id='".$_SESSION['user_id']."' LIMIT 1"); 
      
      $vypis=mysql_fetch_array($vyber);
      
      $aktualne_heslo = $vypis['password'];
      
      if($password != $aktualne_heslo){ 
         
        $backlink="index.php?page=nastavenia&chyba=zmena_hesla";
        
      }elseif($password1 != $password2){
      
      $backlink="index.php?page=nastavenia&chyba=zmena_hesla";
      
      }else{            
      
        $password_novy=md5($password1); 
         
        $VlozData=mysql_query("UPDATE users set password=$password_novy WHERE user_id='".$_SESSION['user_id']."' LIMIT 1") or die (mysql_error());
        	
        $backlink="index.php?page=nastavenia&ok=zmena_hesla"; 
        
      }

    }
  }else{
    $backlink="index.php?page=nastavenia";
  }
 header ("Location: ../$backlink");
ob_end_flush();
?>