title: storing/retrieving IPv4 & IPv6 addresses in MySQL
body: <p>Sorry I don't know much about this subject, but all I'm looking for is a quick-and-easy solution for uniquely representing any IP address (v4/v6) in MySQL so I can easily retrieve the last time (if any) that a particular computer has visited my site.</p>
  
  <p>I don't need to do any computations on the addresses, just retrieval, so any unique representation should be ok.  I do plan on storing a lot of these (don't have an estimate yet), so space may become a concern.</p>
  
  <p>I've seen many solutions for storing IP addresses, but it's unclear which work for both versions.  MySQL's built-in INET_ATON doesn't seem to support IPv6.  PHP's inet_pton seems promising but requires prior knowledge of the address's format.  I'm also unsure about its usage (MySQL field type and writing the insertion statement via PHP).  I've seen varchar(39) used to represent IPv6 addresses as strings, and I like that this solution is somewhat independent of server configuration; however, I'm a little uneasy about disk space.  Would this approach be sufficient for all addresses that $_SERVER['HTTP_CLIENT_IP'] might output?</p>
  
  <p>I'm a little surprised there isn't an obvious generic solution.  I assumed this was a very common task.  I'm having indecision about this single issue, and would like to move on with my project.  Is a quick-and-easy solution unreasonable?</p>
  
  <p>Thanks very much for any guidance...</p>