Version 2.0 introduced the plugin architecture that is used for almost all the customizable functionality of Smarty. This includes: functions modifiers block functions compiler functions prefilters postfilters outputfilters resources inserts With the exception of resources, backwards compatibility with the old way of registering handler functions via register_* API is preserved. If you did not use the API but instead modified the class variables $custom_funcs, $custom_mods, and other ones directly, then you will need to adjust your scripts to either use the API or convert your custom functionality into plugins. Plugins are always loaded on demand. Only the specific modifiers, functions, resources, etc invoked in the templates scripts will be loaded. Moreover, each plugin is loaded only once, even if you have several different instances of Smarty running within the same request. Pre/postfilters and output filters are a bit of a special case. Since they are not mentioned in the templates, they must be registered or loaded explicitly via API functions before the template is processed. The order in which multiple filters of the same type are executed depends on the order in which they are registered or loaded. There is only one plugins directory (for performance reasons). To install a plugin, simply place it in the directory and Smarty will use it automatically. &programmers.plugins.plugins-naming-conventions; &programmers.plugins.plugins-writing; &programmers.plugins.plugins-functions; &programmers.plugins.plugins-modifiers; &programmers.plugins.plugins-block-functions; &programmers.plugins.plugins-compiler-functions; &programmers.plugins.plugins-prefilters-postfilters; &programmers.plugins.plugins-outputfilters; &programmers.plugins.plugins-resources; &programmers.plugins.plugins-inserts;