php 如何准确判断远程文件的扩展名？
http响应头如下：
Array
(
[0] => HTTP/1.1 200 OK
[1] => Content-Length: 345942
[2] => Content-Type: application/octet-stream
[3] => Server: Microsoft-IIS/6.0
[4] => X-Powered-By: ASP.NET
[5] => Date: Sun, 08 Dec 2013 05:44:39 GMT
[6] => Connection: close
)
文件名里面没有扩展名，杂乱无章的。
