Hi,
I am using Enterprise Redhat Linux 2.1 with Apache Web Server.
By extracting phpdig-1.8.0.zip to /usr/local/phpdig/, I had to create a Directory entry in Apache's httpd.conf file, anaologous to creating a virtual directory entry in IIS.
To anyway ensure that was not the problem, I removed the directory entry and moved the phpdig/ folder under the default Apache DocumentRoot at /var/www/html/.
The behaviour is still the same...