PHP: Get Accurate User IP Address

// PHP: Get Accurate User IP Address  
function strFindCorrectIP() {  
    $headers = array(
        'HTTP_CLIENT_IP',
        'HTTP_X_FORWARDED_FOR',
        'HTTP_X_FORWARDED',
        'HTTP_X_CLUSTER_CLIENT_IP',
        'HTTP_FORWARDED_FOR',
        'HTTP_FORWARDED',
        'REMOTE_ADDR'
    );

    foreach ($headers as $key) {
        if (array_key_exists($key, $_SERVER) <mark>= true) {
            foreach (explode(',', $_SERVER[$key]) as $ip) {
                if (filter_var($ip, FILTER_VALIDATE_IP) !</mark> false) {
                    return $ip;
                }
            }
        }
    }
}