PHPのip2long関数とlong2ip関数の実装原理

$ip = '12.34.56.78';
$ips = explode('.', $ip);
$result = 0;
$result += $ips[0]<<24;
$result += $ips[1]<<16;
$result += $ips[2]<<8;
$result += $ips[3];
echo bindec(decbin($result));
echo &#39;<br/>&#39;;
echo bindec(decbin(ip2long($ip)));
echo &#39;<br/>&#39;;

$str = &#39;&#39;;
$str .= intval($result/intval(pow(2, 24))) .&#39;.&#39;;
$str .= intval(($result&0x00FFFFFF)/intval(pow(2, 16))) .&#39;.&#39;;
$str .= intval(($result&0x0000FFFF)/intval(pow(2, 8))) .&#39;.&#39;;
$str .= intval($result&0x000000FF);

echo $str;
echo &#39;<br/>&#39;;
echo long2ip($result);

203569230
203569230
12.34.56.78
12.34.56.78