In a new post to his blog Brandon Savage asks why some of the best development tools don't seem to be written in PHP.

Trac. CruiseControl. phpUnderControl. Jira. Bugzilla. These are all intensely popular development tools. And not a single one of them is written in PHP. Why? [...] Some might argue that PHP is a lesser language, and thus incapable of producing the results that Python and Java can produce. Others might argue that other languages are more mature. But the truth is that these applications don't exist in PHP simply because PHP wasn't previously capable of producing them.

He expresses a desire to work on some of these tools and to make them native to PHP, but several comments on the post steer him towards some projects that have already done this sort of thing including Xinc, ArbitTracker and sismo.