I know that Calibre include a powerful server which can provide HTML and OPDS. But my goal was to host my OPDS server on a small server with limited RAM and CPU (it could also be a VPS). That's why I coded COPS.
It's main advantages are :
- No need for many dependencies (aside from PHP).
- No need for a lot of CPU or RAM.
- Not much code.
- Search is available.
- With Dropbox it's very easy to have an always up to date OPDS server.
- 100% OPDS valid code (checked with http://opds-validator.appspot.com/).
- It was fun to code.
It's still in early stages but it works enough for me. In any cases I'm open to suggestions to enhance it.
You can download it here : http://blog.slucas.fr/en/oss/calibre-opds-php-server