Question

This says $total and $sub is undefined for $total += $sub. $sub was declared in the while loop and both $sub are within the function so it should be a local variable. Why can’t I use it?

public function cart() {
    foreach($_SESSION as $name=>$value){
        if (substr($name, 0, 5) == 'cart_') {
            if((int)$value > 0){
                $id = substr($name, 5, (strlen($name)-5));

                $st = $this->db->prepare("select id, name, price from deals where id=?");
                $st->bindParam(1, $id);
                $st->execute();

                while($cart_item = $st->fetch(PDO::FETCH_OBJ)){
                    $sub = $cart_item->price*$value;
                    echo $cart_item->name.' x '.$value.' @ '.$cart_item->price.' = '.$sub.' <a href="cart.php?add='.$id.'">[+]</a> <a href="cart.php?remove='.$id.'">[-]</a> <a href="cart.php?delete='.$id.'">[Delete]</a><br/>';
                }
            }
        }
        $total += $sub;
    }

}

Answer 1

The $total variable should be initialized above your foreach. The $sub variable should be initialized inside the foreach, at the top.

$total = 0;
foreach ($_SESSION as $name => $value) {
    $sub = 0;
    ...

Also, you can move the $total += $sub; higher up, to be positioned just below the inner while loop.