PHP can be used to generate a lot of addresses and private keys for use with Bitcoin. How about Tor? Can we use PHP to generate a Tor hostname?
If you are asking about 'specific' urls (or custom urls), so to do this with PHP you can let php interface for example Scallion on the server you serve php from (or forward the commands to another computer). I have never seen a 'pure' php way of doing it.
If you just mean random onion domains, then you can let php interface tor through php\python with this library Stem. Let that generate the domains\keys through php commands triggering python.