I've set up 'Uploadify' to upload files to my server where I process them with CodeIgniter's file upload library.
However, I think Uploadify changes the mime type of the files, or does something else weird which causes CodeIgniter to give a 'the file type is not allowed' error despite it being allowed.
E.g I've allowed JPEG files but when I upload them using Uploadify, I get that error.
Is there any workaround for this? Basically, I want only image uploads to be allowed, e.g .jpg, .jpeg, .bmp, .png. Do I have to manually check the extension of the files or is there any better option?
You're correct, uploadify uses the mime type application/octet-stream for most (all?) the files which it uploads. I think this is actually caused by Flash handling the uploading, but I'm not 100% sure.
In your controller where you handle the upload, drop in a print_r($_FILES) and check out what the mime-type is, then just add it to your application/config/mimes.php file.
So in your mimes.php file you'll probably have something like:
'jpg' => array('image/jpeg', 'image/pjpeg', 'application/octet-stream'),
来源：https://stackoverflow.com/questions/6484289/strange-codeigniter-file-upload-error