Compiler functions are called only during compilation of the template. They are useful for injecting PHP code or time-sensitive static content into the template. If there is both a compiler function and a custom function registered under the same name, the compiler function has precedence. mixed smarty_compiler_name string $tag_arg object &$smarty The compiler function is passed two parameters: the tag argument string - basically, everything from the function name until the ending delimiter, and the Smarty object. It's supposed to return the PHP code to be injected into the compiled template. _current_file . " compiled at " . date('Y-m-d H:M'). "';"; } ?> ]]> This function can be called from the template as: The resulting PHP code in the compiled template would be something like this: ]]> See also register_compiler_function(), unregister_compiler_function().