After upgrading all PEAR packages yesterday, OpenID login with phorkie stopped working: The OpenID association request timed out after 3 seconds. Time to investigate the issue.
I was able to create a curl POST request that took 3.6 seconds on my SimpleID instance. With that I was able to track down the functions that were slow with var_dump(); exit(); statements in the code.
I followed the trail from openid_dh_server_assoc() to openid_dh_generate_key_pair() to bignum_powmod() which did some heavy math in vanilla PHP - when PHP's GMP extension is not installed.
Installing Debian's php5-gmp package made it all fast; the login request takes 0.8s now.
To be fair: SimpleID's system requirements document tells us about that issue:
You can also have the following extension enabled for better performance: