Tim Bray - 2008 Prediction 4: PHP Problems:

"A big project I’m peripherally involved with needed to include an outward-facing Wiki, and I suggested that MediaWiki was damn good stuff. They put in quite a bit of work and failed to get MW to integrate with the rest of the system. Yes, it’s a good wiki, but it shouldn’t have been that hard to make it play nice with others, and I got the impression that the PHP-ness of it was a big part of the problem."

I'm not sure where PHP gets in our way when we're trying to write good software...