This is the directory (or directories) where Smarty will look for the
plugins that it needs. Default is
"plugins" under the
SMARTY_DIR. If you
supply a relative path, Smarty will first look under the
SMARTY_DIR, then
relative to the cwd (current working directory), then relative to the PHP
include_path. If $plugins_dir is an array of directories, Smarty will
search for your plugin in each plugin directory in the order they are
given.
Technical Note:
For best performance, do not setup your $plugins_dir to have to use
the PHP include path. Use an absolute pathname, or a path relative
to SMARTY_DIR or the cwd.