Access restriction based on referral?

[cpc]

I have a script that I would like to restrict unless referred by a specific page. If the condition is not met I would like it to display a HTTP/1.0 404 Not Found.

Can anyone assist?

Thank you.

[djjjozsi]

you can recognize on the first read from the $_SERVER['REFERER']

but notice that its not an insurrance that the browser sends a real value and not a fake value. So you should not trust in this value.