function getExtIP(){
        ipURL = 'http://ip.bjango.com/?random='+new Date().getTime();
        ipConnection = new XMLHttpRequest();
        ipConnection.open("GET",ipURL,true);
        ipConnection.onreadystatechange = function() {
                if(ipConnection.readyState == 4 && ipConnection.responseText != null && ipConnection.responseText.length > 0) {
                        extIP = ipConnection.responseText;
                        if(extIP.length < 20 && ipConnection.status == 200 && extIP.match(/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/)){
                                e("wide_extip").innerHTML = extIP;
                                e("tall_extip").innerHTML = extIP;
                                valid_ip = true;
                        } else {
                                valid_ip = false;
                                e("wide_extip").innerHTML = "Unknown";
                                e("tall_extip").innerHTML = "Unknown";
                        }   
                }   
        }   
        ipConnection.send(null);
}

<?php

// Echo back IP address as a "plain text" document
header('Content-type: text/plain');

// Check to see if server has been forwarded the request
if (isset($_SERVER['HTTP_X_REMOTE_ADDR'])) {
	printf("%s\n", $_SERVER['HTTP_X_REMOTE_ADDR']);
} else {
	printf("%s\n", $_SERVER['REMOTE_ADDR']);
}

?>