$re = '/^([[:xdigit:]]{1,4}(?::[[:xdigit:]]{1,4}){7}|::|:(?::[[:xdigit:]]{1,4}){1,6}|[[:xdigit:]]{1,4}:(?::[[:xdigit:]]{1,4}){1,5}|(?:[[:xdigit:]]{1,4}:){2}(?::[[:xdigit:]]{1,4}){1,4}|(?:[[:xdigit:]]{1,4}:){3}(?::[[:xdigit:]]{1,4}){1,3}|(?:[[:xdigit:]]{1,4}:){4}(?::[[:xdigit:]]{1,4}){1,2}|(?:[[:xdigit:]]{1,4}:){5}:[[:xdigit:]]{1,4}|(?:[[:xdigit:]]{1,4}:){1,6}:)$/m';
$str = '::
::123
::123:456
::123:456:789
::123:456:789:abc:def:6666
::123:456:789:abc:def:6666:7
123::456
123::456:789
123::456:789:abc
123::456:789:abc:def
123::456:789:abc:def:6
123::456:789:abc:def:6:7
123:456::789
123:456::789:abc
123:456::789:abc:def
123:456::789:abc:def:6666
123:456::789:abc:def:6666:7
123:456:789::abc
123:456:789::abc:def
123:456:789::abc:def:6666
123:456:789::abc:def:6666:7
123:456:789:abc::def
123:456:789:abc::def:6666
123:456:789:abc::def:66666:7
123:456:789:abc:def::6666
123:456:789:abc:def::6666:7
123:456:789:abc:def:6666::
123:456:789:abc:def::
123:456:789:abc::
123:456:789::
123:456::
123::
123::456:789:abc:def:6666
123:456:789:abc:def:6666:7
123::456::abc
';
preg_match_all($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