PHP Nuke is a portal written in PHP.
I believe it uses a MySQL back-end for data storage, and PHP is quite fast, much more so than Perl.
It's really designed for a relatively large group of individuals who provide content for a site that serves a single purpose. Each individual signs up, gets login, and then has the chance to customize his own page (not what he shows, what he sees when he logs in) created from content provided by himself or others.
It runs best on a unix server (FreeBSD, for instance), with Apache cutomized for PHP support. PHP is a server-side language that is parsed by the web server - and the php commands are sent to the PHP processor which carries out the commands, creates the results, and returns it back to the web server, which then combines it with any static content (html) provided by you.
I investigated a number of portals in recent history, and looked over PHPNuke as one of the options.
I don't see it as being particularly useful to a TDR related group, however. Perhaps you might see some situation where it would be, but I didn't. It is mostly useful in providing a central location which would concentrate information for individual users. However, this data type is mostly HTML pages and links provided by outside information providers like Reuters and so on. It is mostly dependent upon a strongly html and computer oriented as well as highly active userbase to be useful.
Similar and superior is MetaDot, which is far more powerful, but more difficult to get working and very resource intensive.
Tell me what it is that you want to accomplish and I'll suggest some things you could try out.