Forwarding co-domain

[Captain]

Hello!

Want to know how I can forward co-domain to another directory of my server.
For example I have one user who wants to use my hosting but at this time with co-domain test.serverdomain.com.
At this time hi have not domain. But hi want to use DB, PHP and so on.
I created a new client with new site (testdomain.com) and create in hosting panel domain one co-domain test.serverdomain.com and in forward I enter directory of later created client (/var/www/web20/web/)
But forwarding dont work.

How I can to create this system, when user can use hosting without his domain (throw hosting server domain)

Big thnks for help.

[till]

In this case you create a new website for the domain and nota forward.

Create a new website with:

hostname: test
domain: serverdomain.com