Why do clients request .php files my server does not host?

I am running a web server and watching what people request. I have been getting frequent traffic like:

GET /phph/php/ph.php HTTP/1.1

or

GET /mrmr/mrm/mr.php HTTP/1.1

Are these scans? Are the clients checking if my server is already compromised or are they checking if I am vulnerable?

As far as I can tell, since I don't host such directories, such traffic is a scan for compromised machines; I do not know for sure because I think it unsafe to click the links Google provides when I search such things.