Defaulting a Value of a Text Input Field

I've got the following script. It allows a user to input a quantity, then the new price is updated. But there seems to be a code error (in that is doesn't update for the new price).

Can anyone see where the error might be?

Code:

---

<?php
if(isset($_POST["quantity"]))
        $quantity = settype($_POST["quantity"], "integer");
else
        $quantity = 1;

$item_price = 10.99;
printf("%d x item = $%.2f",
        $quantity, $quantity * $item_price);
?>
<FORM ACTION="buy.php" METHOD=POST>
Update quantity:
<INPUT NAME="quantity" SIZE=2
value =<?php echo $quantity;?>">
<INPUT TYPE=SUBMIT VALUE="Change quantity and re-calculate price">
</FORM>

---

settype() is being used incorrectly. It should be:

Code:

---

if(isset($_POST['quantity'])) {
    $quantity = $_POST['quantity'];
    if(!settype($quantity, 'integer'))
        $quantity = 1;
} else {
    $quantity = 1;
}

---

Thanks. That now works!