$trusted_dir is only for use when $security is enabled. This is an array of all directories that are considered trusted. Trusted directories are where you keep php scripts that are executed directly from the templates with {include_php}.
當 $security 開啟時，$trusted_dir 才會是有作用的。此變數的陣列值是所有被 視為可信任的目錄路徑。被視為可信任的目錄路徑下的 php 程式碼都可以使用 {include_php} 標籤直接在樣版中執行。