In a new post today, Ed Finkler shares some interesting stats he's generated based on some NIST NVD data and graphed out. It shows PHP as being in the top 20 list for more insecure applications.
What follows is a breakdown of the 20 PHP-based applications that had the highest aggregate vulnerability scores (NIST assigns a score from 1-10 for the severity of each entry), and the highest total number of vulnerabilities, over the past 12 months. Of the two, I feel that the aggregate score is a better indicator of security issues.
The Excel charts show the total NVD score and the total number of NVD entries for several popular PHP applications (like phpBB, phpMyAdmin, TikiWiki, and Joomla). He also notes that there are some other extenuating circumstances surrounding these numbers (not a level line) and that the trend seems to be more on the side of issues with forums than any other type of PHP application.