How to identify server IP address in PHP

Question

Like this for the server ip:

$_SERVER['SERVER_ADDR'];

and this for the port

$_SERVER['SERVER_PORT'];

If you are using PHP version 5.3 or higher you can do the following:

$host= gethostname();
$ip = gethostbyname($host);

This works well when you are running a stand-alone script, not running through the web server.

for example:

$_SERVER['SERVER_ADDR']

when your on IIS, try:

$_SERVER['LOCAL_ADDR']

I came to this page looking for a way of getting my own ip address not the one of the remote machine connecting to me.

This will not work for a windows machine.

But in case someone searches for what I was looking for:

#! /usr/bin/php
<?php
$my_current_ip=exec("ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'");
echo $my_current_ip;

(Shamelessly adapted from How to I get the primary IP address of the local machine on Linux and OS X?)

Neither of the most up-voted answers will reliably return the server's public address. Generally $_SERVER['SERVER_ADDR'] will be correct, but if you're accessing the server via a VPN it will likely return the internal network address rather than a public address, and even when not on the same network some configurations will will simply be blank or have some other specified value.

Likewise, there are scenarios where $host= gethostname(); $ip = gethostbyname($host); won't return the correct values because it's relying on on both DNS (either internally configured or external records) and the server's hostname settings to extrapolate the server's IP address. Both of these steps are potentially faulty. For instance, if the hostname of the server is formatted like a domain name (i.e. HOSTNAME=yahoo.com) then (at least on my php5.4/Centos6 setup) gethostbyname will skip straight to finding Yahoo.com's address rather than the local server's.

Furthermore, because gethostbyname falls back on public DNS records a testing server with unpublished or incorrect public DNS records (for instance, you're accessing the server by localhost or IP address, or if you're overriding public DNS using your local hosts file) then you'll get back either no IP address (it will just return the hostname) or even worse it will return the wrong address specified in the public DNS records if one exists or if there's a wildcard for the domain.

Depending on the situation, you can also try a third approach by doing something like this:

$external_ip = exec('curl http://ipecho.net/plain; echo');

This has its own flaws (relies on a specific third-party site, and there could be network settings that route outbound connections through a different host or proxy) and like gethostbyname it can be slow. I'm honestly not sure which approach will be correct most often, but the lesson to take to heart is that specific scenarios/configurations will result in incorrect outputs for all of these approaches... so if possible verify that the approach you're using is returning the values you expect.

This is what you could use as an adaptation of the above examples without worrying about curl installed on your server.

<?php
      // create a new cURL resource
      $ch = curl_init ();

      // set URL and other appropriate options
      curl_setopt ($ch, CURLOPT_URL, "http://ipecho.net/plain");
      curl_setopt ($ch, CURLOPT_HEADER, 0);
      curl_setopt ($ch, CURLOPT_RETURNTRANSFER, true);

      // grab URL and pass it to the browser

      $ip = curl_exec ($ch);
      echo "The public ip for this server is: $ip";
      // close cURL resource, and free up system resources
      curl_close ($ch);
    ?>