I did read the doc carefully, and I have some more questions:
The doc says that there could be multiple files in the solutionDir directory, I see that for instance rust-representer only looks for lib.rs. For PHP should I look for only one file (currently I am looking for soltution.php)
About the representation.json, is it just for the version ?
Different tracks take different approaches. One could look for just one file, but that would be incorrect if the student submitted more files (which is valid). What you should probably do is to look at all submitted source files, and then ignore and helper and test files (as defined in the .meta/config.json file’s files key). Does that make sense?