|This is an essay. It expresses the opinions and ideas of some Wikimedians but may not have wide support. This is not policy on Meta, but it may be a policy or guideline on other Wikimedia projects. Feel free to update this page as needed, or use the discussion page to propose major changes.|
When considering a new or existing Web application for Wikimedia-related project development, PHP is preferred.
Better the devil you know than the devil you don't.
While PHP is hardly a perfect programming language, it is the language used by MediaWiki and the language that most of Wikimedia's infrastructure is set up to handle well. Wikimedia technical staff are also most familiar with PHP.
But this cool app is in Python/Perl/Ruby!
Even a mediocre PHP application is better than an application written in Python or Perl or Ruby or any other language. Because of the extensive PHP knowledge that Wikimedia-related folks have, it makes more sense to invest in and improve a mediocre PHP application rather than settling for a better application that happens to be written in a different programming language. The maintenance and overhead costs simply aren't worth the benefit.