title: In PhP How to know the Server IP (the main IP)
body: <p>Before I asked how to  know all the IPs available to the server. What about if I want to know the main IP?</p>
  
  <p>Does a server have a main IP or all IPs are really equal?</p>
  
  <p>Is it in $_SERVER array?</p>
  
  <p>I am not asking about the IP of the host. I am talking about the MAIN IP. Each server has a main IP right among all those many IPs?</p>