", "Hello World", "

"; # get the factorial parameter if it exists if (isset($_GET['factorial'])) { $n = $_GET['factorial']; } else { $n = 20; } echo "

Now I will calculate {$n}!

"; # note use of {} to embed a variable. $fac = 1; for ($i=1; $i <= $n; $i++) { # notice the C-style loop $fac = $fac*$i; echo "{$i}! = {$fac}
"; } ?>