1326ms vs. 1382ms is 60ms, and when normal page load times are somewhere around 200ms, it makes a substantial difference.
Even if we disregard the fact that microtime tests have a big stddev,
We shouldn't do that. The posted results are totally worthless without an error estimate.
People, stop wasting everybody's time, read http://drupal.org/node/79237, or preferably an introduction to statistics and a howto on doing experiments in first year phyiscs, then re-do the tests.
imo the tests are pretty pointless. Given that PHP uses the zend hashtable to store all lists of this type (including constants) then this link shows how the table hash key is generated using the DJBX33A algorithm:- http://lxr.php.net/source/ZendEngine2/zend_hash.h#315 Seems to me that upper or lower case won't have an effect on this (not one that microtime is going to perceive anyhow) so this hardly seems worth following up. If you really feel the "need for speed" then the only suggestion is to keep all constant definitions to 8 characters or less. Hardly practical in the real world. --Andy