verifying a domain using php

Question

I have a member area, where they can add their domains and it will be displayed in the profile page..but now I want to add a verification process, just like google web-masters does..where they need to upload a certain file and so.. please tell me whats the best way to do this ?

Thanks :)

Answer 1

1. Generate a token for each domain (sha-1 of domain or so), store it in your DB or what have you.
2. Generate a text-file containing the token on user request.
3. Ask the user to inform you to poll or poll every now and then to check the URL. This can easily be done by file_get_contents in PHP if fopen_wrappers are enabled.
4. The token is obviously compared to the token in your DB to make sure it wasn't just a random file present at a random domain..
5. Could be a good idea to check at some time interval if the file is still there, to keep someone from selling the domain but remain in control

It's not really black art as we can assume the user has access to its domain once any specific request which proves access can be fulfilled by the user. There's no real way to fool the system except doing some DNS-magic, or gaining entry to the webserver running on the domain, which is out of your control anyway.