Question

Is it possible to detect source of web forwarding?

For example,
Domain A redirects to Domain B where Domain B has PHP hosting?

Basically I would like something like the following:

if ($was_redirected_from_domain_a) { ... }

Answer 1

As @MoarCodePlz and @Christopher Armstrong point out, $_SERVER["HTTP_REFERER"] is the solution.

However, in your specific case, two redirects take place:

http://fhc.quickmediasolutions.com/image/-1457172086.png

This way, the original referrer info is lost. You will need to disable the second redirect, and run your PHP in my-art-gallery.co.uk‘s index page.

Update after seeing the phpinfo() output:

$_SERVER["HTTP_REFER"] is indeed completely non-existent.

I suspect the culprit is this configuration setting:

suhosin.server.strip = On 

your hosting company is running the Suhosin PHP patch, which allows removing certain data from the PHP page for enhanced security. You may need to ask them to activate HTTP_REFERER.

The only other way would be redirecting domain A to something like

domainb.co.uk/index.php?camefrom=domainA

You could then fetch the domainA argument through $_GET["camefrom"] – if the hosting provider’s control panel allows that sort of redirection.