I am actually currently in the process of writing just such a database
system for my school with PHP and MySQL. It's something I plan to make available to the public for free or very low cost once it's finished (theoretically within the next couple of weeks). I have not yet decided what the best way to do this is, i.e. whether I should publish the source code for people to set up on their own server or if I should just allow theatres to set up private databases on my server.
Basically, the idea is this:
There are 3 general areas: Costume Items,
Props, and Shows. Costume Items and
Props areas are just lists of all costume pieces and
props that are in the inventory. Shows allows you to
build prop lists by assigning specific
props to a show, and allows costumes to be created by assigning individual costume items to be part of the costume.
Access control is restricted on 3 levels, Editor (full database access), Reader (read-only access to entire database), and Administrator (full database access plus can create and manage user accounts).
If anybody who is a potential user has ideas for features they would like to
send my way, I'd love to hear them.