PHP获取远程文件的大小，通过ob_get_contents实现

function remote_filesize($uri,$user='',$pw='')
{
 ob_start();
 $ch = curl_init($uri);
 curl_setopt($ch, CURLOPT_HEADER, );
 curl_setopt($ch, CURLOPT_NOBODY, );
 if (!empty($user) && !empty($pw)) {
  $headers = array('Authorization: Basic ' . base64_encode($user.':'.$pw));
  curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
 }
 $okay = curl_exec($ch);
 curl_close($ch);
 $head = ob_get_contents();
 ob_end_clean();
 $regex = '/Content-Length:\s([0-9].+?)\s/';
 $count = preg_match($regex, $head, $matches);
 //qq($head);
 return isset($matches[]) ? $matches[] : 'unknown';
}

注意： $head = ob_get_contents(); 得到的是文件的头部信息：
HTTP/1.1  OK
Server: Tengine
Content-Type: image/jpeg
Content-Length:
Connection: keep-alive
Date: Tue,  Dec  :: GMT
Last-Modified: Tue,  Dec  :: GMT
Expires: Thu,  Jan  :: GMT
Cache-Control: max-age=
Accept-Ranges: bytes
Via: cache37.l2cm9-[,-,H], cache11.l2cm9-[,], kunlun7.cn119[,-,H], kunlun6.cn119[,]
Age:
X-Cache: HIT TCP_MEM_HIT dirn::
X-Swift-SaveTime: Thu,  Dec  :: GMT
X-Swift-CacheTime:
Timing-Allow-Origin: *
EagleId: 1bdd224614512746510381352e