php注册页面验证码，不知道哪儿有异常，每次提交就算验证码打错了，居然也能成功提交

php注册页面验证码，不知道哪儿有错误，每次提交就算验证码打错了，居然也能成功提交。
以下是注册页面的全部代码，每次提交验证码不管是输入正确还是错误，内容都会被成功提交。求解决大家看看代码哪儿有错误。





if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
{
  if (PHP_VERSION   $theValue = get_magic_quotes_gpc() ? stripslashes($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"] == "form1")) {
  $insertSQL = sprintf("INSERT INTO user_zc (username, pass, phonenumber, realname, sex) VALUES (%s, %s, %s, %s, %s)",
  GetSQLValueString($_POST['username'], "text"),
  GetSQLValueString($_POST['pass'], "text"),
  GetSQLValueString($_POST['phonenumber'], "int"),
  GetSQLValueString($_POST['realname'], "text"),
  GetSQLValueString($_POST['select'], "text"));
if ($_POST['yzm'] !== $_SESSION["vocode"]) {
header("location: ". "user_zcsb.php" );
}
  mysql_select_db($database_conn, $conn);
  $Result1 = mysql_query($insertSQL, $conn) or die(mysql_error());

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