Group form elements

Group form elements

I have been looking for this through the net but I have not found the
right solution for my problem. I am working with the stock market. I have
a form in my website, and a part of it needs to be repeated for some
symbols.
Let's say I need to set some properties for each symbol, so I have some
inputs that are the same for every symbol. What I would like to do is
define the fields in some way that once I am processing them in my PHP
script, I can access to the data doing something like this:
$_POST["symbol"]["field"]
I have 3 symbols now, but in the future I will have much more, so I would
like to process the whole thing with a loop instead of having to access
every single field manually (e.g.: $_POST["symbol-field"]).
I have seen there is a tag called FIELDSET that could work, but I don't
get it to work.
Thank you very much.