I just published the latest PHP stats:

• PHP 4.4.x show impressive growth during last month, taking scores of web sites from PHP 4.3.11 and 4.3.10. Users are migrating in spite of BC break.
• PHP 5.x rises again, almost reaching 5%, following the trend of the previous monthes. PHP 5.1, published late during the month, had no time to have impact.
• PHP keep it's level of usage even with complex architectures: domains covering 2 or more IP are even showing a slightly higher usage of PHP: 1% to 38% of total.

There's much more posted on the page, including some graphs showing a very large presence of PHP on the internet, how many users are using what versions, and where the highest concentrations of PHP usage are (by country).