PHP Warning: Division by zero

Question

I\'m learning php and built an experimental form-based calculator (also using html & POST method) that returns values to a table. The calculator is functional when I ent

Answer 1

$diffPricePercent = (($actual * 100) / $itemCost) / $itemQty;

$itemCost and $itemQty are returning null or zero, check them what they come with to code from user input

also to check if it's not empty data add:

if (!empty($_POST['num1'])) {
    $itemQty = $_POST['num1'];
}

and you can check this link for POST validation before using it in variable

https://www.virendrachandak.com/techtalk/php-isset-vs-empty-vs-is_null/