While Smarty was made to contain functions relevant to most common web development needs, there are times when you need to extend it. There are also some cases in which developing a Smarty plug-in is a good idea, because it might save you time or it might make sense to centralize a particular type of functionality into a single function call.

In this chapter, we will go over the process of finding, installing, and using plug-ins in templates, and also give an overview of how to implement your own custom functionality.

Smarty defines a plug-in as any type of custom functionality implemented by third-party developers. Smarty is already distributed with a wide variety of functions, and while some of them are needed by Smarty itself (called built‑in functions), others can be changed to define some extra functionality (called custom functions). Plug-ins, however, are usually associated with totally different functionality not available by default in Smarty.