The transition was relatively painless. [...] What's nice about PHP5 is that it caught some errors that have been lingering in our code: PHP5 no longer allows a function to be defined twice, and some basic variable referencing errors that we missed previously.

They made the move to PHP5 for the latest versions of their applications, but have still stuck with the legacy, PHP4 versions for the time being to give customers a buffer period to make the move themselves. He also mentions changes to the way they make Ajax calls. John is a lead developer for both the ADOdb and PHPLens projects.

I can't say the results of the benchmarks are surprising, but it does give a good idea of where, speed-wise, they really improved things in this new release. There are some stats, though, that didn't make that much of a jump. Those seem to be ones dealing with objects and their handling, though - so there's not that much of a jump there anyway.

He tested all sorts of operations, including working with binary data, string and array functionality, looping (for, foreach, etc), and operators. For each statistic, he provides what the test is doing and what the results are. Testing was done with the PHPLens benchmark suite.