I read in the documentation that php-mysql is required to process. I wonder why. I mean, if I planned to code an app that does not use MySQL, why requiring it ? Specially if the target of the app is some low cost server like the Rhasperry Pi or Sheeva Plug. On a fresh light install of Arch for example, PHP requires more than 100 Mo. MySQL requires about the same. If I planed to use a internal SD memory of the SheevaPlug, which is 512Mo only, it's really a pain in the ass to install MySQL when you do not really need it.
So, do you have a really good reason for this requirement ?