ProDevTips.com has a new tutorial posted today sharing a database replication script they've put together to keep two databases in sync.

After reading up on MySQL replication for a bit I realized that it would go quicker to simply write something in PHP that would sync a subset of tables in one database to exact copies of the same tables in another. Note that the code/SQL [in the example] only works if you replicate from one database to another on the same machine since the main thing here are SQL queries that contain operations/look ups on two databases in the same query.

He includes the code to do the fetch on certain tables (based on a unique key), pushes them into an array and exports them back out into another table. There's also a modification included that makes it work on tables without an auto-increment column.