Change IPv4 to IPv6 string

Question

Sander Steffann mentioned in a previous question of mine:

Addresses like 0000:0000:0000:0000:0000:0000:192.168.0.1 are written as 0000:0000:0000:00

Answer 1

I can't believe I wrote this all out in one go and it worked the first time.

$strIP = '0000:0000:0000:0000:0000:0000:192.168.0.1';
$arrIP = explode(':', $strIP);

if( preg_match('/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/', $arrIP[count($arrIP)-1]) ) {
  $ip4parts = explode('.', $arrIP[count($arrIP)-1]);
  $ip6trans = sprintf("%02x%02x:%02x%02x", $ip4parts[0], $ip4parts[1], $ip4parts[2], $ip4parts[3]);
  $arrIP[count($arrIP)-1] = $ip6trans;

  $strIP = implode(':', $arrIP);
}
echo $strIP; //output: 0000:0000:0000:0000:0000:0000:c0a8:0001

Basically:

1. Explode the string on :
2. Check if the last quad is formatted like an IP4 address
3. Explode the last quad on .
4. Re-print the IP4 octets into two hex quads
5. Replace the IP4 quad with the new ones
6. Implode the array on :.