Are there any computer vision libraries in PHP, or any server-side programming languages?
If not, maybe we can make a list of some -already implemented- methods (Viola Jones face detector, landmark detector etc.) to help someone who wants to implement such a library?
Someone's written a php interface to OpenCV - https://github.com/mgdm/OpenCV-for-PHP, though I haven't tested it.
As you've tagged face detection I'll also mention that someone has written a php interface specifically to the face detection functionality of openCV too; http://www.xarg.org/project/php-facedetect/
Alternatively you could try (and this would probably offer more flexibility);
[Note: this is just a short list; searching e.g. "python image processing" will give more options]
Python
Java
C++
The top answer to this question also has a good discussion, though I'd be careful about using Matlab in this instance as you might fall foul of their licence restrictions.
