Sanatize and filter $_GET and $_POST data that handles arrays and is recursive. http://goo.gl/Fonl6D

filter.php

// Filters data against security risks.
function filter($data) {
  if (is_array($data)) {
    foreach ($data as $key => $element) {
      $data[$key] = filter($element);
    }
  } else {
    $data = trim(htmlentities(strip_tags($data)));
    if(get_magic_quotes_gpc()) {
      $data = stripslashes($data);
    }
    $data = filter_var($data ,FILTER_SANITIZE_STRING);
  }
  return $data;
}