On at least two servers which are running PHP 3.0.9 and 4.0 Beta 3 (respectively), persistant database connections don't notice if the connection has been dropped.

  This means that if you start the DB server, and then start the web server, when the connection is established, everything is fine and dandy. If something happens to the connection (for example, postgres is stopped and restarted) the web server keeps trying to use the connection.

  It displays errors saying that the connection is dead, but keeps trying to reuse it anyway on repeated loads of the page, anyway.

  3 solutions present themselves to me. 

  Test the connection before giving it to the script. Seems best, but would involve extra overhead.

  Automatically close and restart connections after certain types of errors. At least after the scripts complete. This would allow errors to appear, but not continue to repeat indefinatly.

  Reduce the value of 'MaxRequestsPerChild' in Apache, so the connections are not reused for as lengthy a period. This avoids PHP changes, but reduces high load efficiency.