Random Avatar Generator

Question

Possible duplicates:
What is the algorithm used to generate these small images with the gravatar symbol?

StackOverflow seems to have nice, randomly generated avatars for users by default. How to do it (preferably with PHP)?

Answer 1

http://en.gravatar.com/

Answer 2

Gravatar: http://en.gravatar.com/

Here is a link to their php reference implementation: http://en.gravatar.com/site/implement/php