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I want to check via php if someone connects to my site via IPv4 or IPv6.

The client address can be found in $_SERVER["REMOTE_ADDR"] but how to check if it's IPv4 or IPv6 ?

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7 Answers 7

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62

Check for IPv4

$ip = "255.255.255.255"; if(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) { echo "Valid IPv4"; } else { echo "Invalid IPv4"; }

Check for IPv6

$ip = "FE80:0000:0000:0000:0202:B3FF:FE1E:8329"; if(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) { echo "Valid IPv6"; } else { echo "Invalid IPv6"; }

For more, check PHP function filter_vars and list of filters for validation.

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1 Comment

Finally, a native solution
27

You can use this:

function ipVersion($txt) { return strpos($txt, ":") === false ? 4 : 6; }
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7 Comments

On a dual stack server (which is the usual deployment) this will always return 6 because of IPv4-mapped IPv6 addresses. To fix this, also check that the string doesn't begin with ::ffff: (and you probably want to strip that, too).
This is a bit old, but at a glance, I would instead check for "." instead of ":". I know it doesn't make a huge difference when looking at the $_SERVER superglobal or something, but the ":" character CAN appear in other instances of IPv4 connections since it's used to separate the address and the port. An IPv6 string OTOH, with or without a port specified, will never have a dot/period. If that character is present, it's IPv4.
@user3137702 2001:db8::10.0.0.1 is a perfectly valid IPv6 address.
False advice! This string may contain ::ffff:10.20.30.40! It does on my server. It's better to check for the dot . character; it only appears in IPv4. By the way, while kasperd's address is sometimes valid, it is never returned by the server. The dot is really the proof of IPv4 here.
::ffff:10.20.30.40 is not a valid ipv4 it is ipv6 even though it is a mapping for ipv4.
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9

You can use inet_pton:

<?php $packedIp = @inet_pton($ip); if ($packedIp === false) { // invalid IP } else if (isset($packedIp[4])) { // IPv6 } else { // IPv4 }
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6

What about counting the number of '.' and/or ':' in $_SERVER["REMOTE_ADDR"] ?

If there is more than 0 ':', and no '.' symbol in $_SERVER["REMOTE_ADDR"], I suppose you can consider you user is connected via IPv6.


Another solution might be to use the filter extension : there are constants (see the end of the page) that seem to be related to IPv4 and IPv6 :

FILTER_FLAG_IPV4 (integer)
Allow only IPv4 address in "validate_ip" filter.

FILTER_FLAG_IPV6 (integer)
Allow only IPv6 address in "validate_ip" filter.

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Don't assume that if there are '.' it's an IPv4, IPv6 can also contain IPv4-style addresses eg: 0:0:0:0:0:127.0.0.1
4

Since the highest voted answer has a rather significant problem, I'm going to share my own.

This returns true if an address which appears to be IPv6 is passed in, and false if an address which appears to be IPv4 (or IPv4-mapped IPv6) is passed in. The actual addresses are not further validated; use filter_var() if you need to validate them.

function is_ipv6($address) { $ipv4_mapped_ipv6 = strpos($address, "::ffff:"); return (strpos($address, ":") !== FALSE) && ($ipv4_mapped_ipv6 === FALSE || $ipv4_mapped_ipv6 != 0); }
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ipv4 mapped address is still invalid ipv4 address, why would you count it as ipv4?
@CemKalyoncu because from a network point of view, when you have a mapped IPv4, there's no IPv6 in use — so if you need to do a reverse DNS lookup or anything similar, it will have to be an IPv4 one.
If you would do parsing, you will need to apply IPv6 rules. Also incoming channel would be IPv6 even if the sender is using IPv4.
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IPv4 addresses all match the regex /^\d{1,3}(\.\d{1,3}){3,3}$/.

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looks that it does the job. but hey .... it's regular expression! it can do everything, if you just know how...
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You can use AF_INET6 to detect if PHP is compiled with IPv6 support:

<?php if ( defined('AF_INET6') ) { echo 'Yes'; } else { echo 'No'; } ?>
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