Como restar valores de un formulario con php y mysql?

[xagentex]

Formulario.php

Código:

<?php require_once('Connections/conex.php'); ?>
<?php
if (!isset($_SESSION)) {
  session_start();
}
$MM_authorizedUsers = "Nivel 1,Nivel 2";
$MM_donotCheckaccess = "false";

// *** Restrict Access To Page: Grant or deny access to this page
function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) { 
  // For security, start by assuming the visitor is NOT authorized. 
  $isValid = False; 

  // When a visitor has logged into this site, the Session variable MM_Username set equal to their username. 
  // Therefore, we know that a user is NOT logged in if that Session variable is blank. 
  if (!empty($UserName)) { 
    // Besides being logged in, you may restrict access to only certain users based on an ID established when they login. 
    // Parse the strings into arrays. 
    $arrUsers = Explode(",", $strUsers); 
    $arrGroups = Explode(",", $strGroups); 
    if (in_array($UserName, $arrUsers)) { 
      $isValid = true; 
    } 
    // Or, you may restrict access to only certain users based on their username. 
    if (in_array($UserGroup, $arrGroups)) { 
      $isValid = true; 
    } 
    if (($strUsers == "") && false) { 
      $isValid = true; 
    } 
  } 
  return $isValid; 
}

$MM_restrictGoTo = "acceso.php";
if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {   
  $MM_qsChar = "?";
  $MM_referrer = $_SERVER['PHP_SELF'];
  if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";
  if (isset($_SERVER['QUERY_STRING']) && strlen($_SERVER['QUERY_STRING']) > 0) 
  $MM_referrer .= "?" . $_SERVER['QUERY_STRING'];
  $MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);
  header("Location: ". $MM_restrictGoTo); 
  exit;
}
?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
{
  if (PHP_VERSION < 6) {
    $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;
  }

  $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);

  switch ($theType) {
    case "text":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;    
    case "long":
    case "int":
      $theValue = ($theValue != "") ? intval($theValue) : "NULL";
      break;
    case "double":
      $theValue = ($theValue != "") ? doubleval($theValue) : "NULL";
      break;
    case "date":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;
    case "defined":
      $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
      break;
  }
  return $theValue;
}
}

$editFormAction = $_SERVER['PHP_SELF'];
if (isset($_SERVER['QUERY_STRING'])) {
  $editFormAction .= "?" . htmlentities($_SERVER['QUERY_STRING']);
}

if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form")) {
  $insertSQL = sprintf("INSERT INTO autogestion (usuario, operacion, precio, name, cedula, fn, serial, plan) VALUES (%s, %s, %s, %s, %s, %s, %s, %s)",
                       GetSQLValueString($_POST['usuario'], "text"),
                       GetSQLValueString($_POST['operacion'], "text"),
					   GetSQLValueString($_POST['precio'], "text"),
                       GetSQLValueString($_POST['name'], "text"),
                       GetSQLValueString($_POST['cedula'], "text"),
                       GetSQLValueString($_POST['fn'], "text"),
                       GetSQLValueString($_POST['serial'], "text"),
					   GetSQLValueString($_POST['plan'], "text"));

  mysql_select_db($database_conex, $conex);
  $Result1 = mysql_query($insertSQL, $conex) or die(mysql_error());

  $insertGoTo = "listar.php";
  if (isset($_SERVER['QUERY_STRING'])) {
    $insertGoTo .= (strpos($insertGoTo, '?')) ? "&" : "?";
    $insertGoTo .= $_SERVER['QUERY_STRING'];
  }
  header(sprintf("Location: %s", $insertGoTo));
}

mysql_select_db($database_conex, $conex);
$query_sagv = "SELECT * FROM autogestion";
$sagv = mysql_query($query_sagv, $conex) or die(mysql_error());
$row_sagv = mysql_fetch_assoc($sagv);
$totalRows_sagv = mysql_num_rows($sagv);
?>
<!doctype html>
<html>
<head>
<meta charset="utf-8">

<title>Documento sin título</title>
<link href="css/estilos.css" rel="stylesheet" type="text/css">
</head>

<body oncontextmenu="return false">
<div id="formulario">
<div id="encabezado">Activacion de Lineas CDMA y GSM</div>

<form action="<?php echo $editFormAction; ?>" method="POST" name="form" target="link">

<input type="hidden" name="usuario" value="<?php echo $_SESSION['MM_Username']; ?>">
<input type="hidden" name="operacion" value="Activacion de Linea">
<input type="hidden" name="precio" value="4000">

<label id="label_name">Nombre y Apellido:</label>
<input type="text" name="name" placeholder="Nombre y Apellido">

<label id="label_cedula">Cedula de Identidad:</label>
<input type="text" name="cedula" placeholder="Cedula de Identidad">

<label id="label_fn">Fecha de Nacimiento:</label>
<input type="text" name="fn" placeholder="Fecha de Nacimiento">

<label id="label_serial">Serial o Sim Card a Conectar:</label>
<input type="text" name="serial" placeholder="Serial o Sim Card a Conectar">

<label id="label_plan">Seleccione Plan a Activar:</label>
<select name="plan">
  <option value="">Seleccione</option>
  <option value="PLAN CONECTADOS">PLAN CONECTADOS</option>
  <option value="INTELIPLAN 100">INTELIPLAN 100</option>
  <option value="INTELIPLAN 400">INTELIPLAN 400</option>
  <option value="INTELIPLAN 1.2">INTELIPLAN 1.2</option>
  <option value="INTELIPLAN 3.2">INTELIPLAN 3.2</option>
  <option value="BB ULTRA">BB ULTRA</option>
  
</select>

<input name="procesar" type="submit" id="procesar" value="Procesar">
<input  id="cancelar" type="button" value="Cancelar" onclick="location.href = 'listar.php'">


<div id="linea">
<br><font color="red">CONDICIONES:</font><br>
Costo del requerimiento 4000 Bs.<br>
Una vez Procesado el requerimiento<br>
Tiene un Lapso de 24 Horas Para Cancelarlo.<br>
</div>
<input type="hidden" name="MM_insert" value="form">

</form>

</div>
</body>
</html>
<?php
mysql_free_result($sagv);
?>

Espero Pueda Ayudarme.
Saludos