PHPで取得する方法めも。

$url = 'http://example.com';

$res = get_headers($url);

var_dump($res);
↓
array(13) {
  [0]=>
  string(15) "HTTP/1.0 200 OK"
  [1]=>
  string(20) "Accept-Ranges: bytes"
  [2]=>
  string(29) "Cache-Control: max-age=604800"
  [3]=>
  string(23) "Content-Type: text/html"
  [4]=>
  string(35) "Date: Sun, 08 Sep 2013 15:49:42 GMT"
  [5]=>
  string(18) "Etag: "3012602696""
  [6]=>
  string(38) "Expires: Sun, 15 Sep 2013 15:49:42 GMT"
  [7]=>
  string(44) "Last-Modified: Fri, 09 Aug 2013 23:54:35 GMT"
  [8]=>
  string(22) "Server: ECS (sjc/4FCE)"
  [9]=>
  string(12) "X-Cache: HIT"
  [10]=>
  string(20) "x-ec-custom-error: 1"
  [11]=>
  string(20) "Content-Length: 1270"
  [12]=>
  string(17) "Connection: close"
}

get_headers()の第2引数に0以外の値を渡すと、配列のキーに「Content-Type」やら「Content-Length」やらが入ってくれる。

$url = 'http://example.com';

$res = get_headers($url, 1);

var_dump($res);
↓
array(13) {
  [0]=>
  string(15) "HTTP/1.0 200 OK"
  ["Accept-Ranges"]=>
  string(5) "bytes"
  ["Cache-Control"]=>
  string(14) "max-age=604800"
  ["Content-Type"]=>
  string(9) "text/html"
  ["Date"]=>
  string(29) "Sun, 08 Sep 2013 15:52:38 GMT"
  ["Etag"]=>
  string(12) ""3012602696""
  ["Expires"]=>
  string(29) "Sun, 15 Sep 2013 15:52:38 GMT"
  ["Last-Modified"]=>
  string(29) "Fri, 09 Aug 2013 23:54:35 GMT"
  ["Server"]=>
  string(14) "ECS (sjc/4FB4)"
  ["X-Cache"]=>
  string(3) "HIT"
  ["x-ec-custom-error"]=>
  string(1) "1"
  ["Content-Length"]=>
  string(4) "1270"
  ["Connection"]=>
  string(5) "close"
}

関数の定義は以下の通り。

array get_headers(string $url [, int $format = 0 ])

どこかで使えそうだったので一応メモ。