And digg probably had a similar error, since it makes no sense for php to be any faster in sorting than mysql. The statement here isn't that a sort in php is 4

And digg probably had a similar error, since it makes no sense for php to be any faster in sorting than mysql. The statement here isn't that a sort in php is 4000% faster than a sort in mysql, all things equal. What is left out of the discussion is the fact that all things are likely not equal, their database servers are way more resource constrained / under heavier load than the web servers. Thus, a CPU-bound operation like sorting will perform better if you can move the operation to a server that has more of the resource in question available.