function makePromoCodes($num = 10, $exp_date = 3)
{
$code_exp_date = time() + 86400 * $exp_date;
$pr = new PlaceOrder();
for ($i = 0; $i <= $num; $i++) {
$code = $pr->generateRandomString();
$query = "insert into mdl_promo_code " . "(code,active,expire_date) " . "values ('" . $code . "',\n '1', \n '" . $code_exp_date . "')";
echo "Query: " . $query . "<br/>";
$this->db->query($query);
}
}