Функция:

function protection($string) {

$string = trim($string);

if (isset ($string)) {

$string = htmlspecialchars($string);

}

else {

$string = NULL;

}

return $string;

}

Пример использования (SQL):

$_GET['age'] = (int) abs($_GET['age']);

$_GET['country'] = (string) protection($_GET['country']);



if (isset ($_GET['age'], $_GET['country'])) {

mysql_query(sprintf('SELECT * FROM `users` WHERE `age` = "%d" AND `country` = "%s"', $_GET['id'], $_GET['country']));

}

else {



}