I have no idea what is causing this issue, but it seems to be related to the displayed file (just a simple index.php to print phpinfo) being in an aliased directory. Any suggestions what I can do to avoid the warning?
Here's an excerpt from my httpd.conf:
<Directory "<dir with broken php>"> Options Indexes FollowSymLinks ExecCGI Includes AllowOverride All Order allow,deny Allow from all </Directory> Alias /smartersoftware/ "<broken dir>" <FilesMatch \.php$> SetHandler application/x-httpd-php </FilesMatch>
The last three lines were required to make php work at all (which I found a bit strange, and it may or may not be related to my problem).
AddType application/x-mapp-php5 .php didn't change anything.