You will need PHP5. At least as from the pPHPlib versions as
of 2.0.0 and higher.
The library itself is architecture indepandant,
however we develop mostly on Linux systems thus we cannot really test
the features on other architectures. But we develop with
cross-platform-interoperability in mind. Still then, there might
be some features which you cannot use under windows, like IPC.
In principle you do not need any databases to use the pPHPlib. But
as for the supported database we recommand MySQL. Also for the
reasons above: We mostly
use this DB in our daily work. However the API is designed that you
can easily add your own DB interface for any other DB. And if you
would like to do so, you are greatly welcome!
Why did we make de decision to only support as from PHP 5?
The pPHPlib is heavly object oriented. And because the OO support
in PHP versions older than 5 was severely lacking, we decided to
make the drastic move and upgrade the pPHPlib to version 2, which
no longer will provide support for the older versions (esp 4).