My hosting-provider provides for compatibility resons both php-version 4 and 5 on the servers.
.php is processed by version 4 and .php5 by the php 5 parser.
So the Piwik files are by default processed as php4, wich won’t work.
This only works on Apache Server and the use of .htacces files has to be allowed.
You can always try to see if it works.
Make a file with the file-name: .htaccess
Containing: AddType application/x-httpd-php5 .php
This rule tells the Apache-server application to proces .php-files in the folder containing the .htaccess file with the php version 5 parser.
Save this file and upload it into the piwik directory on your web-server.