如何将字符串变量转换为int并同时添加两个整数？

Question

This is my code:

    <?php
    //for reference
    $intqty = (int) $_POST["qty_input"];
    (int)$_SESSION['cart_qty'] += $intqty;
    ?>

The $_POST['qty'] is a string and I'm trying to add and store the values in a session variable and its not working. The output of when I echo $_SESSION['cart_qty']; is 0;

Answer 1

If $_POST["qty_input"] is not valid number, casting to int will return 0.

$_SESSION['cart_qty'] = (int)$_SESSION['cart_qty'] + $intqty;