PHP默认文本输入字段的值

Question

In this code, it should change the quantity, but its not changing. its always setting the value '1'.

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

$item_price = 5.99;
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">
</FORM>
</body>
</html>

Answer 1

settype is used to set type of variable, it returns bool value indicating success or failure. You need to assign $_POST value to $quantity (with type cast), try this:

if(isset($_POST["quantity"])) {
  $quantity = (int)$_POST["quantity"];
} else {
  $quantity = 1;
}

// or
$quantity = isset($_POST["quantity"]) ? (int)$_POST["quantity"] : 1;