- substr: documentation ( source)
- round: documentation ( source)
<?php
$width = 2500 / 1000;
$height = 1500 / 1000;
$price = "£10.00";
$price_var = substr($price, 2);
$quantity = (round($width,2)) * (round($height,2));
echo (round($quantity,2) * $price_var);