hello I integrated the membership subscription in the website, but I fail to insert data to the database.

checking out all the function I make a txt file with php with data and generates me correctly.

but I can not verify any data and less insert.

        <?php

          // read the post from PayPal system and add 'cmd'
          $req = 'cmd=_notify-validate';

          foreach ($_POST as $key => $value) 
          {
                $value = urlencode(stripslashes($value));
                $req .= "&$key=$value";
          }

          // Post back to PayPal system to validate
          $header .= "POST /cgi-bin/webscr HTTP/1.0\r\n";
          $header .= "Content-Type: application/x-www-form-urlencoded\r\n";
          $header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
          $fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);

          // Assign posted variables to local variables
          $item_name        = $_POST['item_name'];
          $item_number      = $_POST['item_number'];
          $payment_status   = $_POST['payment_status'];
          $payment_amount   = $_POST['mc_gross'];
          $payment_currency = $_POST['mc_currency'];
          $txn_id           = $_POST['txn_id'];
          $receiver_email   = $_POST['receiver_email'];
          $payer_email      = $_POST['payer_email'];
          $user_id          = $_POST['custom'];

//Here i make the txt file and it works correctly
//but after this does not work or make a txt file

    //Insert and update data
    if (!$fp) 
    {
    // HTTP ERROR
    } 
    else 
    {

    fputs ($fp, $header . $req);

          while (!feof($fp)) 
          {
                $res = fgets ($fp, 1024);

                if (strcmp ($res, "VERIFIED") == 0) 
                {
                      //Verificamos el estado del pedido
                      if ($payment_status == 'Completed') 
                      {
                            $txn_id_check = mysql_query("SELECT Transaction_ID FROM ".$db_table_prefix."Users_Payments WHERE Transaction_ID='".$txn_id."'");
                            if (mysql_num_rows($txn_id_check) !=1) 
                            {
                                  //Si el pago se ha realizado al dueño especificado y coincide con el dueño
                                  if ($receiver_email == $website_Payment_Email) 
                                  {
                                        //Tipo de cuenta segun pagado
                                        if ($payment_amount == '10.00' && $payment_currency == 'EUR') 
                                        {

                                        //add txn_id to database
                                        $log_query = mysql_query("INSERT INTO `".$db_table_prefix."Users_Payments` VALUES ('','".$txn_id."','".$payer_email."')");

                                        //update premium to 3
                                        $update_premium = mysql_query("UPDATE ".$db_table_prefix."Users SET Group_ID='3' WHERE User_ID='".$user_id."'");

                                        }
                                  }
                            }            
                      }
                }
                else if (strcmp ($res, "INVALID") == 0) 
                {
                // log for manual investigation
                }
          }

    fclose ($fp);

    }
    ?>

I call this file with require_once () with the connection to the database

any ideas?

thanks