The open source PHP project site was compromised earlier today. The site appears to have been compromised and had some of its Javascript altered to exploit vulnerable systems visiting the website. Google's stop-badware system caught this as well and flagged php.net
as distributing malware, warning users whose browsers support it not to
visit the site. The comment by a Google employee over at the hacker news thread (official Google webmaster forum thread) seems to suggest that php.net wasn't incorrectly flagged.