validation engine convert negative number to positive number - php

Question

how can I enter only positive number and if I entered negative number it will convert automatically to positive number this the code That I have how can I edit it
<?php
if (isset($_SESSION["cart_products"]) && count($_SESSION["cart_products"]) > 0) {
echo '<div class="cart-view-table-front" id="view-cart">';
echo '<h3>Your Shopping Cart</h3>';
echo '<form method="post" action="cart_update.php">';
echo '<table width="100%" cellpadding="6" cellspacing="0">';
echo '<tbody>';
$total = 0;
$b = 0;
foreach ($_SESSION["cart_products"] as $cart_itm) {
$product_name = $cart_itm["product_name"];
$product_qty = $cart_itm["product_qty"];
$product_price = $cart_itm["product_price"];
$product_code = $cart_itm["product_code"];
$product_color = $cart_itm["product_color"];
$bg_color = ($b++ % 2 == 1) ? 'odd' : 'even'; //zebra stripe
echo '<tr class="' . $bg_color . '">';
echo '<td>Qty <input type="text" size="3" maxlength="3" name="product_qty[' . $product_code . ']" value="' . $product_qty . '" /></td>';
echo '<td>' . $product_name . '</td>';
echo '<td><input type="checkbox" name="remove_code[]" value="' . $product_code . '" /> Remove</td>';
echo '</tr>';
$subtotal = ($product_price * $product_qty);
$total = ($total + $subtotal);
}
echo '<td colspan="4">';
echo '<button type="submit">Update</button>Checkout';
echo '</td>';
echo '</tbody>';
echo '</table>';
$current_url = urlencode($url = "http://" . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
echo '<input type="hidden" name="return_url" value="' . $current_url . '" />';
echo '</form>';
echo '</div>';
}
?>

Answer 1

GrumpyCrouton > What is the variable that you are trying to convert to positive?
M.Alhaddad > #GrumpyCrouton product_qty
It's quite simple.
Just use abs() on the variable.
$product_qty = abs($cart_itm["product_qty"]);
Note: abs() works in (PHP 4, PHP 5, PHP 7)
"Converting a number to positive" is just getting it's absolute value.
Documentation:
PHP function.abs