Neznámý problém v kódu (500 error)

<?php
/*************************************************/
/*                                               */
/*     MOBILE PAYMENT PROCESSING                 */
/*        Author: Josef Burger; http://jobu.cz   */
/*        Copyright: (c) Josef Burger            */
/*        Version: 1.0                           */
/*        Relase: 2012-02-12                     */
/*                                               */
/*************************************************/
// Based on B:CMS Libraries and BLC (Burger Library Core)




// IP Protect  [195.47.87.160 - 195.47.87.191]
//    Simple protect, all unauthorized access are abborted

/*  $ip = $_SERVER['REMOTE_ADDR'];
  $ip_e = explode('.', trim($ip));

  $ip_end = (int)$ip_e[3];
  unset($ip_e[3]);
  $ip_ch = implode('.', $ip_e);
  if(!($ip_ch == '195.47.87' and (($ip_end >= 160) and ($ip_end <= 191)))) {exit('spatna ip');}

       */



// URL decode
  if(empty($_GET['text']) or empty($_GET['price'])) exit('chybi text ci price (get) parametr'); // Base protection
  $user = $_GET['text'];
  $user = str_replace('pm+merver+','',$_GET['text']);
  $price = (int)$_GET['price'];
  




// Edit user to VIP user
  require_once '_config.php';
  require_once 'i_database.php';
  require_once 'c_mysql.php';
  
  $db = new Mysql();
  define('_timestamp', date('Y-m-j H:i:s')); define('_ts', _timestamp); // TimeStamp
  define('end_ts', date('Y-m-j H:i:s', strtotime('+'.$vip_time[$price].' day')));

  $db->q("UPDATE `permissions_inheritance` SET `vip-end-time` = '".end_ts."', `parent` = '"._parent_vip."' WHERE `child` = '$user'");
  $response = "Dekujeme $user, platbu jsme prijali a VIP Vam bude brzy aktivovano. Merver.cz";
  Header ("Content-type:text/plain");
  Header ("Content-length".strlen($response));
  echo $response;
  exit(200);

?>