Different browsers, different IPs?

Question

I'm saving the user's IP addresses by saving the value of $_SERVER['REMOTE_ADDR'] in a MySQL database. Problem is that for both Firefox and Chrome $_SERVER['REMOTE_ADDR'] is ::1 (that means localhost in IPv6) and for IE and Opera is 127.0.0.1 (IPv4).

So, my questions are

• Are IP versions browser-dependant? (I used to think it depended on the computer)

• Should I create two fields in the database, one for IPv4 addresses and one for IPv6 ones?

• Should I unify all IPs to IPv6? And how can I do this in PHP (if it's even possible)?

Answer 1

1. Fairly obvious - your box is IPv6-enabled, Firefox/Chrome use IPv6 whenever available, while IE and Opera don't (or it's a off-by-default setting).

2. Store the address in a string that's long enough to hold an IPv6 address.

3. No, 'cause in the general case you cannot.

Answer 2

Use the PHP function inet_pton to convert human readable IP addresses to their packed representation. You can then store each IP address in a BINARY(16) or VARBINARY(16) field in your database.

Answer 3

The browser will use whatever is available. This can be IPv4 or IPv6, and that can even change during the session. On top of that keep in mind that a host can have many IPv6 addresses so it might change during the session as well.

In short: don't depend on the value of REMOTE_ADDR too much :-)