Is There A Way?
*PHPbb. No. Unless it's on a windows computer (which is usually very rare) and the person you're giving it to is stupid enough to put it on their server box, or if it's on a linux computer and you've made your own nifty keylogger and manage to get it on there. Either way, this would be relatively pointless because people dont usually type stuff on server boxes, 'cept for maintenance and such. But yeah, look into a less shitty way of getting a password or remote access.
Now if you're talking about actually putting it in the code of the forum/board…. then that's stupid. If you had access to change the code, why not just change the forms to email it to your email or even just make an include exploit and use the stolen hashes.
P.S. You dont need to capitalize every word in your sentence.