http://www.firstworks.com/sqlrelay.html SQL Relay is a persistent database connection system supporting ODBC, Oracle, MySQL, mSQL, PostgreSQL, Sybase, MS SQL Server, DB2, Interbase, Lago and SQLite with C, C++, Perl, Python, Zope and PHP APIs, command line clients and a GUI configuration tool. It is ideal for speeding up database-driven web-based applications, accessing databases from unsupported platforms, migrating between databases, distributing access to replicated databases and throttling database access.
I'm trying to evaluate it now -- but what looks pretty cool are the result set buffering control (PHP buffers the entire result set in memory, regardless of you fetching it or not), result set caching -- do I hear vB template caching any one? -- suspending and resuming sessions to span things over multiple pages (this helps standardize your SQL so if you need to port something you don't have to worry about MySQL's LIMIT x, y stuff).
The only thing that annoys me is that I can't find a precompiled .so file. As much as I enjoy downloading 3 different sets of support libraries and then compiling them, it would be nice to offer a .so file so that I don't have to waste my time making everything work. The most annoying part is that if they are of the "release early, release often" crowd that means I have to go through the process every day or so to get the latest fixes.
Questions to think about:
Why use this over PHP's DB libraries?
Does their method of "connection pooling" offer any advantage to PHP's persistent DB connections?