Nope, your PHP was wrong.
PHP would be essentially the same
for ( $n = 50; $n <= 57; ++$n )
If you don't have short tags enabled in PHP, you'd have to do
<form id="<?php echo n; ?>">
Which is pretty much equivalent to ASP's
<form id="<% response.write n %>">
But thankfully, unlike PHP, ASP *always* enables short tags, so you CAN do just