Worth a read for couple of reasons. Sitepoint's standards for content are high. Harry has also written some great stuff on PHP coding. He is the author of Sitepoint's new PHP book, and has his own excellent PHP site: phpPatterns().
Again ... if coding isn't your thing this won't interest you in the slightest!
Wow ... I have done a bit of reading on PHP5 already (mainly the whole object oriented programming angle), but the article I cited below alerted me to something I had not read about elsewhere. Evidently PHP5 will include its own lightweight database engine - SQLite. I can see plenty of applications for fast and simple database functionality even used in conjunction with MySQL or Postgresql.
I had an application the other day where I wanted to cache a result set from a reasonably complex MySQL query in a temporary table for faster retrieval second time round ... sounds like this would offer even faster retrieval.
Having said this there is some discussion (and link to discussion) of limitations here ...