I have a Piwik site hosted on linux with:Apache 2.2.26; PHP version: 5.4.22; MySQL version: 5.5.36-cll;
I have used the automatic upgrade routine from the message on my piwik site. The upgrade started; the screen cleared; nothing else; no error messages.
Looking at the directories, most of the php and js files have zero length.
Something similar happened last time. I ended up installing from scratch, but that then removed all my data.