Making php use specific network interface / IP

Question

TL;DR: Is there a runtime or php.ini directive for IP/network interface?

Setup: Debian, NginX, php-fpm

The machine has multiple IPs configured in the network interfaces. Each virtual host in NginX is listening to a specific IP. If there is any networking related action performed by PHP, for example a cURL call, the default IP is used every time. If I set CURLOPT_INTERFACE manually in a script, the correct ip is being used, but I need to do this automatically somehow via NginX vhost and php-fpm handshake.

So, site1.com get's called, somehow it needs to pass the ip that that site is listening on to the php-fpm and php-fpm needs to set it as the network interface to use for any Internet connections php will make during execution, be it cURL, get_file_contents(), or any other function.

Can this be done?

Thanks

Answer 1

To answer your TLDR, no that can't be done in PHP itself. There is no global setting that can be changed for all outbound traffic like file_get_contents/etc. As you stated you can customize the interface for curl and several other packages/ components, but there's nothing to globally set it.

Mark Strosberg's answer should work for curl!

Answer 2

In your Nginx configuration, you can add this, setting the number to the desired IP.

 fastcgi_param CURLOPT_INTERFACE 1.2.3.4; 

This will populate the $_SERVER variable inside the PHP script.

In your PHP script, set CURLOPT_INTERFACE to $_SERVER['CURLOPT_INTERFACE'];

I've not tested this, but I think it should work.