It can be written as follows :-

    class uuidgen
    {
        function uuid($serverID=1)
        {
            $t=explode(" ",microtime());
            return sprintf( '%04x-%08s-%08s-%04s-%04x%04x',
                $serverID,
                $this->clientIPToHex(),
                substr("00000000".dechex($t[1]),-8),   // get 8HEX of unixtime
                substr("0000".dechex(round($t[0]*65536)),-4), // get 4HEX of microtime
                mt_rand(0,0xffff), mt_rand(0,0xffff));
        }
        function uuidDecode($uuid)
        {
            $rez=Array();
            $u=explode("-",$uuid);
            if(is_array($u)&&count($u)==5)
            {
                $rez=Array(
                    'serverID'=>$u[0],
                    'ip'=>$this->clientIPFromHex($u[1]),
                    'unixtime'=>hexdec($u[2]),
                    'micro'=>(hexdec($u[3])/65536)
                );
            }
            return $rez;
        }
        function clientIPToHex($ip="")
        {
            $hex="";
            if($ip=="")
            {
                $ip=getEnv("REMOTE_ADDR");
            }
            $part=explode('.', $ip);
            for ($i=0; $i<=count($part)-1; $i++)
            {
                $hex.=substr("0".dechex($part[$i]),-2);
            }
            return $hex;
        }
        function clientIPFromHex($hex)
        {
            $ip="";
            if(strlen($hex)==8)
            {
                $ip.=hexdec(substr($hex,0,2)).".";
                $ip.=hexdec(substr($hex,2,2)).".";
                $ip.=hexdec(substr($hex,4,2)).".";
                $ip.=hexdec(substr($hex,6,2));
            }
            return $ip;
        }
    }

To get uuid call the class as follows :-

$x=$uuid->uuid();
echo $x