php losing 2 decimal

i have two number qty_p and price_db. qty_p will be always int. and price_db can be int or double with 2 decimal place.

$qty_p = $_POST['qty'];
$price_db = $row['price'];

on top iam get the value and so far its fine.

but below the php is round the number up and losing the 2 decimals. can any one explain to me why its doing that. is there a function that can i use?

$total = $price_db * $qty_db;