$re = '/^(?:(?:[a-f0-9]*)?:){1,7}[a-f0-9]*$/im';
$str = '2001:db8:3333:4444:5555:6666:7777:8888
2001:db8:3333:4444:CCCC:DDDD:EEEE:FFFF
::
2001:db8::
::1234:5678
2001:db8::1234:5678
2001:0db8:0001:0000:0000:0ab9:C0A8:0102
2001:db8:1::ab9:C0A8:102
::1
asdlkjkjd:asldjlaskdjlkja:lasdkjlkajsd:';
preg_match_all($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