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<?php function convertIPv6To4($ip) { // validate if given IP is a proper IPv6 address if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) === false) { // validate if given IP is a proper IPv4 address if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) === false) { // ip address is invalid return ''; } return $ip; } // check if ip is a masked IPv4 address if (substr($ip, 0, 7) == '::ffff:') { $ip = substr($ip, 7); if (preg_match('~^([a-f0-9]{1,4}):([a-f0-9]{1,4})$~', $ip, $matches)) { $ip = array( base_convert($matches[1], 16, 10), base_convert($matches[2], 16, 10) ); $ipParts = array(); $tmp = $ip[0] % 256; $ipParts[] = ($ip[0] - $tmp) / 256; $ipParts[] = $tmp; $tmp = $ip[1] % 256; $ipParts[] = ($ip[1] - $tmp) / 256; $ipParts[] = $tmp; return implode('.', $ipParts); } else { return $ip; } } else { // given ip is an IPv6 address and cannot be converted return $ip; } } echo convertIPv6To4('2003:66:4f14:d880:7075:9457:3857:29ec')