i think you have not updated codeigniter setup properly from 2.2 to 3.1.6 because file upload is not working in the setup please have a look into that i have updated the mime.php in config folder still not working error i am getting is
file type is not allowed when i have define type in config array.
$config = array(
'upload_path' => "./assets/images/profile",
'allowed_types' => "image/jpg|image/png|image/jpeg",
'overwrite' => false,
'max_size' => "1000",
'remove_spaces' => true
);
here i have define the jpg,png,and jpeg but i cant upload any of image file.