Web scripting languages, such as PHP and JavaScript, provide a wide range of dynamic features that make
them both flexible and error-prone. In order to prevent bugs in web applications, there is a sore need for
powerful static analysis tools. In this paper, we investigate how Abstract Interpretation may be leveraged
to provide a precise value analysis providing rich typing information that can be a useful component for
such tools.
In particular, we define the formal semantics for a core of PHP that illustrates
type juggling
, the implicit
type conversions typical of PHP, and investigate the design of abstract domains and operations that, while
still scalable, are expressive enough to cope with type juggling. We believe that our approach can also be
applied to other languages with implicit type conversions.