Help with redirect

Hello i have this code from what i can see as long as the referrer is blank it will redirect however what i want is for it to also redirect if the referrer is from a certain domain. Not just a site but any link from an entire domain. Also how would i add multiple domains. Thanks

<?php

	$referer = $_SERVER['HTTP_REFERER'];
	if($referer =="")
	{

		echo "<meta http-equiv=\"refresh\" content=\"0;url=http://www.adomain.com\">";

	}

?>

Code (markup):

 

You can try this one

<?php

// Put the domains here
$domains = array('yahoo.com', 'google.com', 'fbi.gov');

$referer = $_SERVER['HTTP_REFERER'];

// Loop for each domain
foreach ($domains as $dom) {
	if (stristr($referer, $dom)) {// match
		exit("<meta http-equiv=\"refresh\" content=\"0;url=http://www.adomain.com\">");
	};
};

?>

PHP:

 

Thanks man