$re = '/(?:^|\s)(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]+|::(ffff(:0{1,4})?:)?((25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{0,2}|[1-9]?\d))(?=\s|$)
/im';
$str = '{1: Initial address, regex should say valid/match}
2001:0db8:0000:0000:0000:ff00:0042:8329
{2: After removing all leading zeroes, regex should say valid/match}
2001:db8:0:0:0:ff00:42:8329
{3: After omitting consecutive sections of zeroes, regex should say valid/match}
2001:db8::ff00:42:8329
{4: The loopback address, regex should say valid/match}
0000:0000:0000:0000:0000:0000:0000:0001
{5: The loopback address be abbreviated to ::1 by using both rules, regex should say valid/match}
::1
{6: This should be valid, regex should say valid/match}
ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:192.168.158.190
{7: This should NOT be valid/match}
::
{These two formats allows IPv6 applications to communicate directly with IPv4 applications, regex should say valid/match}
{8}
0:0:0:0:0:ffff:192.1.56.10
{9}
::ffff:192.1.56.10/96
{These next two formats are used for tunneling. It allows IPv6 nodes to communicate across an IPv4 infrastructure, regex should say valid/match}
{10}
0:0:0:0:0:0:192.1.56.10
{11}
::192.1.56.10/96
{These 4 should be valid/match}
{12}
::FFFF:129.144.52.38
{13}
::129.144.52.38
{14}
::FFFF:d
{15}
1080:0:0:0:8:800:200C:417A
{These 4 should NOT be valid/match}
{16}
::FFFF:d.d.d
{17}
::FFFF:d.d
{18}
::d.d.d
{19}
::d.d';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php