If you don't want to add a virtual IP You can use the same IP address, set up a virtual host and make use of the host header instead:
Options -Indexes FollowSymLinks MultiViews
allow from all
CustomLog /home/myname/mywebdirectory/logs/access.log combined
This assumes you want to call the testarea with the url 'testarea' or 'testarea.local', that you are putting your html/php files in /home/myname/mywebdirectory/www and want seperate logs in /home/myname/mywebdirectory/logs (the directories must exist)
To make this resolve so a browser can reach 'testarea' or 'testarea.local' edit your hosts file on the machine you want to use to browse it and add a line like:
192.168.1.10 testarea testarea.local
This assumes 192.168.1.10 is the IP of the server. You could so this with DNS if you are running a local DNS server.
This method require you to set up either a hosts or dns entry for the virtual server, but it has the advantage that random people browsing the IP on port 80 will be served the main sight and not your test area. This can be spoofed but requires knowledge of the correct host header. I would also limit the IP's that can access this test server as it is a common attack vector for crackers to look for broken or partially installed web applications.
Hope that expands on the options a little.