php判断远程文件或网站是否能打开

//默认效果
print_r(get_headers("http://www.baidu.com/img/baidu_sylogo1.gif"));
结果：
Array
(
[0] => HTTP/1.1 200 OK
[1] => Date: Thu, 02 Jun 2011 02:47:27 GMT
[2] => Server: Apache
[3] => P3P: CP=" OTI DSP COR IVA OUR IND COM "
[4] => Set-Cookie: BAIDUID=7F6A5A2ED03878A7791C89C526966F3A:FG=1; expires=Fri, 01-Jun-12 02:47:27 GMT; max-age=31536000; path=/; domain=.baidu.com; version=1
[5] => Last-Modified: Thu, 20 Jan 2011 07:15:35 GMT
[6] => ETag: "65e-49a41e65933c0"
[7] => Accept-Ranges: bytes
[8] => Content-Length: 1630
[9] => Cache-Control: max-age=315360000
[10] => Expires: Sun, 30 May 2021 02:47:27 GMT
[11] => Connection: Close
[12] => Content-Type: image/gif
)

//加参数1的效果
print_r(get_headers("http://www.baidu.com/img/baidu_sylogo1.gif", 1));

结果：
Array
(
[0] => HTTP/1.1 200 OK
[Date] => Thu, 02 Jun 2011 02:49:28 GMT
[Server] => Apache
[P3P] => CP=" OTI DSP COR IVA OUR IND COM "
[Set-Cookie] => BAIDUID=4D875812FC482C0ADE4F5C17068849EE:FG=1; expires=Fri, 01-Jun-12 02:49:28 GMT; max-age=31536000; path=/; domain=.baidu.com; version=1
[Last-Modified] => Thu, 20 Jan 2011 07:15:35 GMT
[ETag] => "65e-49a41e65933c0"
[Accept-Ranges] => bytes
[Content-Length] => 1630
[Cache-Control] => max-age=315360000
[Expires] => Sun, 30 May 2021 02:49:28 GMT
[Connection] => Close
[Content-Type] => image/gif
)
怎么样，get_headers函数还是不错的吧，不过既然效率有问题，那只好不优先考虑了，curl就不错，下面看看curl的做法

function check_remote_file_exists($url)
{
$curl = curl_init($url);
// 不取回数据
curl_setopt($curl, CURLOPT_NOBODY, true);
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, 'GET'); //不加这个会返回403，加了才返回正确的200，原因不明
// 发送请求
$result = curl_exec($curl);
$found = false;
// 如果请求没有发送失败
if ($result !== false)
{
// 再检查http响应码是否为200
$statusCode = curl_getinfo($curl, CURLINFO_HTTP_CODE);
if ($statusCode == 200)
{
$found = true;
}
}
curl_close($curl);

return $found;
}

$exists = check_remote_file_exists('http://www.baidu.com/img/baidu_sylogo1.gif');
echo $exists ? '存在' : '不存在';

$exists = check_remote_file_exists('http://www.baidu.com/test.jpg');
echo $exists ? '存在' : '不存在'