This is to allows you to test domains to see if they match a url based rule list. This has "regex" matching in it to detect any subdomain `*.example.com` and block others using `!ebay.com`.

whitelist_domains.php

<?php

$authDomains = [
    "google.com", // Allow
    "*.google.com", // Allow [Any].google.com
    "!webconsole.google.com", // Block
    "club.hosting.com", // Allow
    "webcome.go.google.com" // Allow
];

$websiteURL = "webconsole.google.com";

echo $websiteURL."<br />";
print( allowedDomain($authDomains, $websiteURL)?"200":"403" );

/**
 * Allowed Domains
 *
 * @param Array    Domain List/Rules
 * @param String   Domain in Question to match, This can be a Domain or a URL.
 * @param Boolean  Have all of the domains blocked unless specified by the rules.
 * @return Boolean Is the Domain allowed based on the Conditions of the List
 */
function allowedDomain($domainList = array(), $domain, $blacklistAll = false){
	// Get the Domain
	$parseUrl = parse_url(trim($domain)); 
	if(isset($parseUrl['host'])) {
		$host = $parseUrl['host'];
	}
	else {
		$path = explode('/', $parseUrl['path']);
		$host = $path[0];
	}
	$h = trim($host);

	// Processing of the URL and the Domain List
	$allowed = $blacklistAll;
	foreach($domainList as $i => $d){
		//echo $allowed?"Yes|<br />":"No|<br />";
		//echo $d."<br />";
		
		// Check to see if this rule is an any. *.example.com
		if($d[0] == "*"){
			removePrefix($d, "*"); // Remove *
			removePrefix($d, "."); // Remove .
			if(endswith($h, $d) == $d){
				$allowed = true;
			}
		}
		
		// Check to see if this is a blocking rule for a a specfic domain,
		// Keep in mind that this is really only good when an entire domain
		//  uses a *. and you want to block one domain of it.
		else if($d[0] == "!"){
			removePrefix($d, "!"); // Remove !
			if($h == $d){
				$allowed = false;
			}
		}
		
		// Basic Rule of matching an exact domain.
		else {
			if($d == $h){
				$allowed = true;
			}
		}    
	}
    return $allowed;
}

function removePrefix(&$str, $prefix = ""){
	if (substr($str, 0, strlen($prefix)) == $prefix) {
		$str = substr($str, strlen($prefix));
	} 
}

/**
 * @link https://stackoverflow.com/a/619725/5779200
 */
function endswith($string, $test) {
    $strlen = strlen($string);
    $testlen = strlen($test);
    if ($testlen > $strlen) return false;
    return substr_compare($string, $test, $strlen - $testlen, $testlen) === 0;
} 

?>