存储应用程序相关配置文件的位置?

we have an svn with several php applications in it (not depending from each other, with different versions).

The problem I have, is that I don't know where to store the config files and how to make them accessible to the applications. Configuration files can of course change between different environments (dev, test, prod) and have password, usernames and url of api's in them.

Checking them in into the SVN, is therefore not a good idea, because people developing and testing should not see the credentials of the productive system.

So this leaves me with storing them outside of the svn tree.

Because I do not want to copy the same config to several versions of an application, I want to use the SetEnv directive of Apache to store the path to the config files.

Syntax: app-name_config-file-name

This will leave me with a lot of environment variables in the Apache configuration-file.

This solution doesn't seem to be the best way. Is there anything better than this?