At the auto-upgrade is a new feature of 2.7, I had never been able to test this functionality, although I had high expectations of it since the plugin upgrade has worked so well.

After searching the forums and Google for a while I found bassmadrigal’s solution – modify .htaccess for the WordPress installation in question and add:

AddType x-mapp-php5 .php

Works fine, and the auto upgrade of plugins stills works too.

The science bit

Using 1and1 as a host requires this directive in .htaccess as detailed in the WordPress codex. It forces the 1and1 server to parse .php files as php5 files (instead of, presumably, php4).

I had this before my upgrade to 2.7 (OK, technically a re-installation) and unfortunately the baby got thrown out with the bathwater.