PHPcurl, a dedicated network interface

Question

I have a (webserver) server with two network interfaces. The first is a standard interface for a public Internet connection and the other is a virtual VPN network interface.

Now I want to send POST data via curl on other web services inside the VPN network.

How can I say that the php there must use the VPN network interface to call that address?

Answer 1

Documentation lists CURLOPT_INTERFACE as a configurable option.

curl_setopt($ch, CURLOPT_INTERFACE, "XXX.XXX.XXX.XXX");