title: Convert IPV4 to IPV6 php
body: <p>is there any way to covert IPV4 to IPV6 format Or vice-versa ? 
   When user registered or login to my site I am storing IP address in database.
   sometimes user's IPV6 formatted address storing.
   User's authentication is checking on ip address column. But next time user's   IPV4 formatted ip address is getting. So that in database I am not getting this IPV4 ip because stored IPV6 address previously.  and authentication of user is going to fail. So I want to convert IPV4 to IPV6. </p>
  
  <p>Thanks.</p>