We were recently looking for an open source light-weight database web administration tool that would be preferably database cross-platform and would work on either ASP.NET or PHP. Adminer fit the bill.
Adminer is written in PHP.
It supports, out of the box PostgreSQL, MySQL, SQLite2 and SQLite3, and even SQL Server and Oracle. This covers most of the databases we commonly use.
Here we'll go over some other features we liked about it that are rare in other web database administration tools.