Question : PHP Statement that shows a percentage of a price

I am trying to display a price in my magento php site that would be charged to customers after a discount coupon is applied. The coupon will give 10% off the original RRP that is stored in the stores database and the only code that I have access to is <?php echo $this->getPriceHtml($_product, true) ?>

What do I need to add to this code to display the price to two decimal places that they would pay with a 10% discount please.

I.e

RRP £100.00 (this is the database price)
With coupon discount £90.00 (new price from PHP statement)

I can do the text bit but the PHP bit has me stuck

Answer : PHP Statement that shows a percentage of a price

Change
$discprice = 0.9 * $match[0];
to
$discprice = sprintf("%.2f", 0.9 * $match[0]);