The php version come with uniform server v15.0.2 is 5.3.8. I want to use an older version 5.2.x.

You'll need to download an earlier version of uniformserver then. They are still available on sourceforge. Once you've got that, you can pick n mix the bits you want. For instance in my US setup I have mysql but I also have a newer version of mariadb running on a different port for a database that I couldn't downgrade - I got that by downloading a newer version and copying it out into my older version. You can do that with php, the email servers etc. Nothing about my original uniformserver is the same as it was - I've customised all of it.

For what its worth, you're not the only one who prefers the older versions. I still use an old 5.2 installation myself. The reason being is that te newer versions require the c++ distributable and if you're using US portably on another computer, you might not have permissions to install it. The older version of US just runs - no dependencies, no registry dust, no installs nothing - it just works.