I just spent many hours wrestling with CodeIgniter. For one thing, it seems to go out of its way to hide PHP errors from you, even in development mode, and even when you try to turn everything back on manually with directives in your index.php.
This doesn’t help when you are trying to integrate AJAX file uploads, and can’t figure out why all you ever get is a ‘500 Server Error’, with no indication of where that error is occurring.
For the record, my problem was that I needed to use CI’s
form_open_multipart() function, in order to get the hidden CSFR protection token. Without it, the Security class was just silently dying before ever getting to my controller’s action handler.