这段取真实 IP 代码有没有需要优化或改进的地方?

欢迎各位大佬批评指正。。谢谢
if (isset($_SERVER)) {
 	// Use $_SERVER variables by preference
 	$HTTP_VARS = $_SERVER;
} else if (isset($_ENV)) {
 	// Fallback to PHP environment variables
 	$HTTP_VARS = $_ENV;
} else $HTTP_VARS = array();

// Step through the captured $_SERVER or $_ENV array, ignoring the case of the keys.
// (Some "authorities" indicate that the keys can be lower or mixed case!)
$ipAddrList = 'unknown';
foreach($HTTP_VARS as $key => $value) {
 	$key = strtoupper($key);
	$value = str_replace(' ', '', $value);// Get rid of embedded blanks

	if ($key == 'HTTP_FORWARDED') {
		// We're dealing with the new HTTP Forwarded: by=identifier; for=identifier; host=host; proto=protocol
		// See: https://tools.ietf.org/html/rfc7239
	    $value = str_replace(',for=', ',', strtolower($value));	// Make everything lower-case and then get rid of extraneous "for=" tags
	    $params = explode(';', $value);// Separate the Forwarded: parameters into an array
	    foreach ($params as $key => $value) {
		    if (substr($value,0,4) == 'for=') {
			    $ipAddrList = substr($value,4);// Everything after "for=" is now a comma-separated list of IPv4 or IPv6 addresses
			    break;
		    }
	    }
	    break;
    }
	if ($key == 'HTTP_X_FORWARDED_FOR') {
	    $ipAddrList = $value;
	    break;
    }
	if ($key == 'HTTP_X_FORWARDED') {
	    $ipAddrList = $value;
	    break;
    }
	if ($key == 'HTTP_FORWARDED_FOR') {
	    $ipAddrList = $value;
	    break;
    }
	if ($key == 'HTTP_CLIENT_IP') {
	    $ipAddrList = $value;
	    break;
    }
	if ($key == 'REMOTE_ADDR') {
	    $ipAddrList = $value;
	    break;
    }
}

$ip = preg_replace('~,.*~', '', $ipAddrList);	// Trim everything after the first comma, leaving just the first IPv4 or IPv6 address

$ip = str_replace(array('"', "'"), '', $ip);	// Get rid of quotation marks used in some addresses
if (substr($ip,0,1) == '[') {
	$ip = preg_replace('~\]:.*~', '', $ip);	// Get rid of IPv6 port number that follows closing square bracket
	$ip = str_replace(array('[', ']'), '', $ip);	// Get rid of square brackets enclosing IPv6 address
} else {
	$ip = preg_replace('~:.*~', '', $ip); // Get rid of IPv4 port number that follows last digit of address
}

unset($HTTP_VARS, $key, $value, $params, $ipAddrList); // We don't need this any more
$_SERVER['REMOTE_ADDR'] = $ip;