How do I get the external IP of my server using PHP?

Just query a host that returns your IP address:

$externalContent = file_get_contents('http://checkip.dyndns.com/');
preg_match('/Current IP Address: \[?([:.0-9a-fA-F]+)\]?/', $externalContent, $m);
$externalIp = $m[1];

or, set up a service that simply echoes just the IP, and use it like this:

$externalIp = file_get_contents('http://yourdomain.example/ip/');

Set up the service yourself by simply echoing the remote IP address, or pay someone to host it. Do not use somebody else's server without permission. Previously, this answer linked to a service of mine that's now being hit multiple times a second.

Note that in an IP network with one or more NATs, you may have multiple external IP addresses. This will give you just one of them.

Also, this solution of course depends on the remote host being available. However, since there is no widely implemented standard (no ISP and only some home routers implement UPnP), there is no other way to get your external IP address. Even if you could talk to your local NAT, you couldn't be sure that there isn't another NAT behind it.

I'm going to add a solution because the others weren't quite right for me because they:

• need to be run on a server with a domain name e.g. gethostbyname() (if you think about it, you don't actually have the problem if you know this a priori)
• can't be used on the CLI (rely on something in $_SERVER to be set by a web server)
• assume a specific format of ifconfig output, which can include multiple non-public interfaces
• depend on parsing someone's website (who may disappear, change the URL, change the format, start lying to you, etc, all without notice)

This is what I would suggest:

$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
$res = socket_connect($sock, '8.8.8.8', 53);
// You might want error checking code here based on the value of $res
socket_getsockname($sock, $addr);
socket_shutdown($sock);
socket_close($sock);

echo $addr; // Ta-da! The IP address you're connecting from

The IP address there is a Google public DNS server. I trust they'll be around and running it for a while. It shouldn't really matter what address you use there as long as its a public IP address that belongs to someone who doesn't mind random connection attempts too much (yourself maybe?).

This is based on an answer I came across when I had a similar problem in Python.

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P.S.: I'm not sure how well the above would work if there is sorcery going on between your machine and the internet.

You could parse it from a service like ip6.me:

<?php

// Pull contents from ip6.me
$file = file_get_contents('http://ip6.me/');

// Trim IP based on HTML formatting
$pos = strpos( $file, '+3' ) + 3;
$ip = substr( $file, $pos, strlen( $file ) );

// Trim IP based on HTML formatting
$pos = strpos( $ip, '</' );
$ip = substr( $ip, 0, $pos );

// Output the IP address of your box
echo "My IP address is $ip";

// Debug only -- all lines following can be removed
echo "\r\n<br/>\r\n<br/>Full results from ip6.me:\r\n<br/>";
echo $file;

There is NO way to get your underlying IP Address that has been designated by your ISP via conventional PHP if you are using a router. A way to get the external IP is to find a service that will obtain it for you and echo the address back to you. I found a handy service which does just that. http://ipecho.net/

You can use:

$realIP = file_get_contents("http://ipecho.net/plain");