Detect parent domain name via script in iframe

[LacyW1997]

I am currently have i an iframe eg:\[code\]<iframe src="http://stackoverflow.com/questions/13737468/www.mydomain.com/myfram.php">\[/code\] and embedded to my client page with different domain name.i want my script in \[code\]"myfram.php"\[/code\] to detect parent domain(client domain) where my iframe is embedded in.I use \[code\]$_SERVRE['SERVER_NAME']\[/code\] but it return my domain name not client. So do you have another ways to grab client domain.