Wordpress: An error occurred in the upload

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.

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.

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.