从我读过的文件中,如果从头部请求中指定的日期起,GET的远程文件已被修改,它将返回200 OK状态.如果没有被修改,它应该返回304未修改.

所以我的问题是,如果服务器不支持“If-Modified-Since”但仍然返回200 OK？

那里有几个工具检查你的网站是否支持“If-Modified-Since”,所以我想我在问他们如何工作.

编辑：

我使用Curl进行了一些测试,发送以下内容;

curl_setopt($ch,CURLOPT_HTTPHEADER,array("If-Modified-Since: ".gmdate('D,d M Y H:i:s \G\M\T',time()+60*60*60*60)));
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch,CURLOPT_FOLLOWLOCATION,CURLOPT_MAXREDIRS,5);
curl_setopt($ch,CURLOPT_HEADER,CURLOPT_NOBODY,CURLOPT_AUTOREFERER,CURLOPT_FORBID_REUSE,CURLOPT_CONNECTTIMEOUT,4);
curl_setopt($ch,CURLOPT_TIMEOUT,4);

即将来google.com的日期返回;

HTTP/1.0 304 Not Modified
Date: Fri,05 Feb 2010 16:11:54 GMT
Server: gws
X-XSS-Protection: 0
X-Cache: MISS from .
Via: 1.0 .:80 (squid)
Connection: close

如果我发

curl_setopt($ch,time()-60*60*60*60)));
curl_setopt($ch,4);

即过去的日期,google.com返回;

HTTP/1.0 200 OK
Date: Fri,05 Feb 2010 16:09:12 GMT
Expires: -1
Cache-Control: private,max-age=0
Content-Type: text/html; charset=ISO-8859-1
Server: gws
X-XSS-Protection: 0
X-Cache: MISS from .
Via: 1.0 .:80 (squid)
Connection: close

如果我发送两个bbc.co.uk(不支持它);

未来一回

HTTP/1.1 200 OK
Date: Fri,05 Feb 2010 16:12:51 GMT
Server: Apache
Set-Cookie: BBC-UID=84bb66bc648318e367bdca3ad1d48cf627005b54f090f211a2182074b4ed92c40ForbSoft%20Web%20Diagnostics%20%28URL%20Validator%29; expires=Tue,04-Feb-14 16:12:51 GMT; path=/; domain=bbc.co.uk;
Accept-Ranges: bytes
Cache-Control: max-age=0
Expires: Fri,05 Feb 2010 16:12:51 GMT
Pragma: no-cache
Content-Length: 111677
Content-Type: text/html

过去的日期返回;

HTTP/1.1 200 OK
Date: Fri,05 Feb 2010 16:14:01 GMT
Server: Apache
Set-Cookie: BBC-UID=841b66ec44232cd91e81e88a014a3c5e50ed4e20c0e07174c4ff59675cd2fa210ForbSoft%20Web%20Diagnostics%20%28URL%20Validator%29; expires=Tue,04-Feb-14 16:14:01 GMT; path=/; domain=bbc.co.uk;
Accept-Ranges: bytes
Cache-Control: max-age=0
Expires: Fri,05 Feb 2010 16:14:01 GMT
Pragma: no-cache
Content-Length: 111672
Content-Type: text/html

所以我的问题依然存在.