Wordpress: An error occurred in the upload - wordpress

Question

After updating to WordPress 3.5, I started getting the following error when uploading files using the Add Media button as a non-admin user:
Error: An error occurred in the upload. Please try again later.
The image seems to finish uploading, but right at the end this error message appears.
This doesn't happen for the administrator, only the other roles. I've even tried giving the other role full admin capabilities, but the error still appears.
Is this a bug? Or am I missing something?

Answer 1

After much trial and error, I finally found a solution that worked for me.
First, I found the following role capabilities to be required to upload files for custom user roles:
$capabilites = array(
'read' => true,
'upload_files' => true,
'edit_published_pages' => true,
'edit_others_pages' => true
);
I'm not sure why these are specifically required, but the error kept occurring without them.
Second, I had to update a function I was using to prevent non-admin users from accessing the Dashboard:
function redirect_nonadmin_fromdash(){
if($_SERVER['PHP_SELF'] == '/wp-admin/async-upload.php'){
/* allow users to upload files */
return true;
} else if(get_user_role() != 'administrator'){
/* custom function get_user_role() checks user role,
requires administrator, else redirects */
wp_safe_redirect(home_url());
exit;
}
}
add_action( 'login_form_login', 'redirect_nonadmin_fromdash' );
add_action( 'admin_init', 'redirect_nonadmin_fromdash', 1 );
Previously, I was checking for the media-upload.php, but the new media uploader uses async-upload.php.
So, essentially, this allows non-admin users to use the new media uploader from the front-end without allowing them access to the Dashboard.
It also restricts their access to the Media Library, which was also important to me.

Answer 2

This could be caused by a couple of different factors, what this usually suggests is:
File is to large
Refeer to this thread on how to up the maximum allowed filesize.
Not enough diskspace
Check if your servers harddrive is full.
Insufficient write permissions
Make sure that PHP and your webserver has write permissions to the wp-uploads folder.

Answer 3

I just had this error after updating PHP to 5.3. The problem on me was short_open_tag.
It was off by default. I enabled it and all is OK now.

Answer 4

I resolve my problem with,
sudo apt-get update
sudo apt-get install php5-gd
this message i get in firebug inspect in moment of upload.
GD Library Error: imagecreatetruecolor does not exist - please contact your webhost and ask them to install the GD libraryGD Library Error: imagecreatetruecolor does not exist - please contact your webhost and ask them to install the GD library{"success":true,"data":{"id":17,"title":"yoshi","filename":"yoshi1.jpg"
so i get this in firebug in moment of upload.

Answer 5

Please see this link for more details - it helped me https://sebastian.expert/fix-wordpress-an-error-occurred-in-the-upload-please-try-again-later/
Basically what it says is to use Developer tools in Chrome or Firefox to see the response from async_upload.php file after uploading files (when error message appears). It returns error details in JSON format. Having details it will be easier and a lot faster to resolve the problem.