2

Using PHP, I need to check if a string contains an IPv6 address - and then extract that IPv6 address if it does.

I've got a regex that is matching a string if it's exactly an IPv6:

$matches = [];
$regex = '/^(((?=.*(::))(?!.*\3.+\3))\3?|([\dA-F]{1,4}(\3|:\b|$)|\2))(?4){5}((?4){2}|(((2[0-4]|1\d|[1-9])?\d|25[0-5])\.?\b){4})\z/i';
preg_match($regex, $ipv6, $matches);

What I'm stuck with is being able to add a wildcard on either side, so I can match things like:

Ultimately I need to do this so I can wrap square brackets around an IPv6 address, so it conforms to RFC 3986 (e.g http://[2001:0db8:85a3:0000:0000:8a2e:0370:7334]/something/page.html).

gbuckingham89
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  • What you can do without fully describing the IPv6 syntax in a pattern is to use `parse_url` (When the scheme is a number then add a fake scheme to obtain the correct host) and `filter_var`. – Casimir et Hippolyte Sep 07 '17 at 21:16

4 Answers4

1

You don't need difficult to read and understand regex in order to verify if a string is a valid IPv6 address. The PHP function filter_var() can do the heavylifting for you:

echo(filter_var('2001:0db8:85a3:0000:0000:8a2e:0370:7334', FILTER_VALIDATE_IP));
# 2001:0db8:85a3:0000:0000:8a2e:0370:7334

echo(filter_var('2001:0db8:85a3::8a2e:0370:7334', FILTER_VALIDATE_IP));
# 2001:0db8:85a3::8a2e:0370:7334

echo(filter_var('192.168.0.1', FILTER_VALIDATE_IP));
# 192.168.0.1

var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_IPV6));
# bool(false)

It returns the input value if it is valid (according to the filter passed as the second argument and the options passed as the third argument) or FALSE otherwise.

If the IP address is the domain of an URL then the PHP function parse_url() can be used to extract it:

print_r(parse_url('http://2001:0db8:85a3:0000:0000:8a2e:0370:7334/something/page.html'));
# Array
# (
#     [scheme] => http
#     [host] => 2001:0db8:85a3:0000:0000:8a2e:0370:7334
#     [path] => /something/page.html
# )

The last string in your example (2001:0db8:85a3:0000:0000:8a2e:0370:7334/something/page.html) is not an URL. It is just some random text that happens to look like an incomplete (and invalid) URL. I don't have a simple solution for it :-(

axiac
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0

You need to use another regexp like this:

(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))

After it, you can wrap ipv6 in your link:

<?php
$ipv6 = 'http://2001:0db8:85a3:0000:0000:8a2e:0370:7334/something/page.html';
$matches = [];
$regex = '(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))';
if (preg_match($regex, $ipv6, $matches)) {
    $result = str_replace($matches[0], '[' .  $matches[0] . ']', $ipv6);
}
Denniselite
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0

Brief

I haven't fully tested the code so I can't be 100% sure it works, but, I ran it against a few different URLs and it seems to be working correctly.

I've taken parts of these answers:

Answer

Answer with domain names

This is what I've come up with:

(?(DEFINE)
  (?<scheme>[a-z][a-z0-9+.-]*)
  (?<userpass>([^:@\/](:[^:@\/])?@))
  (?<domain>[a-z0-9]+(-[a-z0-9]+)*(\.[a-z0-9]+(-[a-z0-9]+)*)+)
  (?<ip>(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])))
  (?<host>((?&domain)|(?&ip)))
  (?<port>(:[\d]{1,5}))
  (?<path>([^?;\#]*))
  (?<query>(\?[^\#;]*))
  (?<anchor>(\#.*))
)
^(?:(?&scheme):\/\/)?(?&userpass)?(?<address>(?&host))(?&port)?\/?(?&path)?(?&query)?(?&anchor)?$

Follow this link to see it in use

Answer without domain names

The above regex will match URLs containing valid domains (whether it be a domain name or address). If you want to match only IP addresses, use the following regex (which includes a simple change in the definition group named host - I removed the reference to the definition group named domain)

(?(DEFINE)
  (?<scheme>[a-z][a-z0-9+.-]*)
  (?<userpass>([^:@\/](:[^:@\/])?@))
  (?<domain>[a-z0-9]+(-[a-z0-9]+)*(\.[a-z0-9]+(-[a-z0-9]+)*)+)
  (?<ip>(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])))
  (?<host>(?&ip))
  (?<port>(:[\d]{1,5}))
  (?<path>([^?;\#]*))
  (?<query>(\?[^\#;]*))
  (?<anchor>(\#.*))
)
^(?:(?&scheme):\/\/)?(?&userpass)?(?<address>(?&host))(?&port)?\/?(?&path)?(?&query)?(?&anchor)?$

Follow this link to see it in use

For those who like a nice long non-legible query you can use the following regex which is equivalent to the one above.

^(?:[a-z][a-z0-9+.-]*:\/\/)?(?:[^:@\/](?::[^:@\/])?@)?(?<address>(?:[0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|(?:[0-9a-fA-F]{1,4}:){1,7}:|(?:[0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|(?:[0-9a-fA-F]{1,4}:){1,5}(?::[0-9a-fA-F]{1,4}){1,2}|(?:[0-9a-fA-F]{1,4}:){1,4}(?::[0-9a-fA-F]{1,4}){1,3}|(?:[0-9a-fA-F]{1,4}:){1,3}(?::[0-9a-fA-F]{1,4}){1,4}|(?:[0-9a-fA-F]{1,4}:){1,2}(?::[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:(?:(?::[0-9a-fA-F]{1,4}){1,6})|:(?:(?::[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(?::[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(?:ffff(?::0{1,4}){0,1}:){0,1}(?:(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9])|(?:[0-9a-fA-F]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9]))(?::[\d]{1,5})?\/?(?:[^?;\#]*)?(?:\?[^\#;]*)?(?:\#.*)?$

Note: Both answers use the i (case insensitive) and x (ignore whitespace) modifiers

ctwheels
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maybe 2 regex match will be better for this. because your regex seems complicated

$regex1 = '/^https?:\/\/([a-z0-9:]{39})/';

if( preg_match( $regex1, $your_text, $matches1) ) {

    $regex2 = '/[a-z0-9]{4}:?/';

    if( preg_match_all( $regex2, $matches1[1], $matches2 ) === 8 )
        echo $your_text.' qualifies!!'; 
}
Gai Kuroda
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