codeigniter 3.1.10 index.php code is not concise,duplicate code in many. $application_folder = strtr( rtrim($application_folder, '/\\'), '/\\', DIRECTORY_SEPARATOR.DIRECTORY_SEPARATOR ); Why not deal with it in one place? for example: arr=[dir1,dir2,dir3]; foreach($arr as $k=>$v) { $arr[$k]= strtr( rtrim($v, '/\\'), '/\\', DIRECTORY_SEPARATOR.DIRECTORY_SEPARATOR }