HTTP::headでレスポンスヘッダのステータスを参照します。
require_once “PEAR.php”;
require_once “HTTP.php”;
$res = HTTP::head( URL );
$res[response_code] == 200 ならOK
print_r($res) はこんな風になります。
Array
(
[response_code] => 200
[response] => HTTP/1.0 200 OK
[Age] => 475
[Date] => Sun, 23 Sep 2007 08:09:31 GMT
[Content-Length] => 5734
[Content-Type] => image/jpeg
[Server] => Apache
[Last-Modified] => Mon, 04 Dec 2006 06:26:44 GMT
[ETag] => “2ee2d88-2b45-4573bfa4”
)