Using html-style tags to define a variable

I recall seeing a thread along these lines previously, but the search functionality at lists.php.net is currently offline, and try as I might to save messages that may prove useful to me in the future, I cannot get them all. So I apologize that this may be found elsewhere, or may be rehash for most of you. That given, I'm looking for the ability (using regex, i'm sure) to put something like <foo>booger</foo> into a database (via a form), and have it translate to $foo="booger" when php sucks it back out. the eventual use of this will allow me to type something like: that's very <m-w>tenacious</m-w> of you ... and have the end output be ereg_replaced (or such) to: that's very <a href=http://www.m-w.com/cgi-bin/dictionary?va=tenacious>tenacious</a> of you ... so i need to take whatever is within the <mw> tag, define that as $word, and then replace the whole string (tags and word) with: <a href="http://www.m-w.com/cgi-bin/dictionary?va=$word>$word</a> follow me? a simple answer will do, or a point towards an appropriate turorial may serve me better in the long run thanks in advance --kevin