write a php function to check if it's called by a domain from the whitelist, it will shows its content

//php
function check_domain($domain) {
    $domains = ['google.com', 'yahoo.com'];
    foreach ($domains as $one) {
        if (strpos($domain, $one) !== false) {
            return true;
        }
    }
    return false;
}

if (check_domain($_SERVER['HTTP_REFERER'])) {
    //show content
}