Identifying and locating interference issues in PHP applications: the case of WordPress

The large success of Content management Systems (CMS) such as WordPress is largely due to the rich ecosystem of themes and plugins developed around the CMS that allows users to easily build and customize complex Web applications featuring photo galleries, contact forms, and blog pages. However, the design of the CMS, the plugin-based architecture, and the implicit characteristics of the programming language used to develop them (often PHP), can cause interference or unwanted side effects between the resources declared and used by different plugins. This paper describes the problem of interference between plugins in CMS, specifically those developed using PHP, and outlines an approach combining static and dynamic analysis to detect and locate such interference. Results of a case study conducted over 10 WordPress plugins shows that the analysis can help to identify and locate plugin interference, and thus be used to enhance CMS quality assurance.