On the PHPClasses.org blog there's a new post talking about a zeitgeist he's created (Manuel Lemos) based on the searching and demand from the PHPClasses.org site.
PHP Zeitgeist is an initiative somewhat similar to Google Zeitgeist. The main difference is that it is based on the statistics of searches performed by PHP developers on the PHPClasses site. Maybe it would be more accurate to call it PHPClasses Zeitgeist, as only part of the PHP community uses the PHPClasses site to search what they need.
Their zeitgeist is split up by keyword and year to show the top searched terms for that time. He lists out some of the top search topics of the past few years (from 2001 through 2009) with the direct links to the results for each.