让浏览器发送 If-None-Match 和 If-Modified-Since
我的浏览器不会
在我的脚本发送的第一个请求上为 PHP 生成的内容发回 If-Modified-Since 标头：
(Status-Line) HTTP/1.1 200 OK
Date Thu, 21 Jan 2010 08:55:25 GMT
Server Apache/2.2.11 (Win32) PHP/5.2.9-1
X-Powered-By PHP/5.2.9-1
Pragma no-cache
x-ua-compatible IE=8;FF=3;OtherUA=4
Last-Modfied Sat, 02 Jan 2010 02:02:20 GMT
Content-Length 28453
Etag b98e0795b509be20146f58e06fbb624f
Keep-Alive timeout=5, max=90
Connection Keep-Alive
Content-Type image/png
在它发送的第二个请求上：
(Request-Line) GET /kincumberunitingchurch/banner_image.php?id=1 HTTP/1.1
Host localhost
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.0.17) Gecko/2009122116 Firefox/3.0.17
Accept image/png,image/*;q=0.8,*/*;q=0.5
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost/kincumberunitingchurch/index.php?sid=tgl9jq3f71nau3cj9vps6pna03
Cookie sid=tgl9jq3f71nau3cj9vps6pna03; PHPSESSID=m0jvven6d7l65pl6odm9ecfnt4
If-None-Match b98e0795b509be20146f58e06fbb624f
Cache-Control max-age=0
对于服务器首先发送的其他文件：
(Status-Line) HTTP/1.1 200 OK
Date Thu, 21 Jan 2010 08:55:25 GMT
Server Apache/2.2.11 (Win32) PHP/5.2.9-1
Last-Modified Wed, 30 Dec 2009 02:40:58 GMT
Etag "1000000013d35-40d9-47be9117f6280"
Accept-Ranges bytes
Content-Length 16601
Keep-Alive timeout=5, max=84
Connection Keep-Alive
Content-Type image/png
并且我的浏览器在下一个请求：
(Request-Line) GET /kincumberunitingchurch/img/cbuttons.png HTTP/1.1
Host localhost
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.0.17) Gecko/2009122116 Firefox/3.0.17
Accept image/png,image/*;q=0.8,*/*;q=0.5
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost/kincumberunitingchurch/mystyle.css
Cookie sid=tgl9jq3f71nau3cj9vps6pna03; PHPSESSID=m0jvven6d7l65pl6odm9ecfnt4
If-Modified-Since Wed, 30 Dec 2009 02:40:58 GMT
If-None-Match "1000000013d35-40d9-47be9117f6280"
Cache-Control max-age=0
为什么会发送 If-Modified-Since 标头
My Browser isn't sending back an If-Modified-Since Header for PHP generated Content
on the first request my script sends:
(Status-Line) HTTP/1.1 200 OK
Date Thu, 21 Jan 2010 08:55:25 GMT
Server Apache/2.2.11 (Win32) PHP/5.2.9-1
X-Powered-By PHP/5.2.9-1
Pragma no-cache
x-ua-compatible IE=8;FF=3;OtherUA=4
Last-Modfied Sat, 02 Jan 2010 02:02:20 GMT
Content-Length 28453
Etag b98e0795b509be20146f58e06fbb624f
Keep-Alive timeout=5, max=90
Connection Keep-Alive
Content-Type image/png
it on the second request it sends:
(Request-Line) GET /kincumberunitingchurch/banner_image.php?id=1 HTTP/1.1
Host localhost
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.0.17) Gecko/2009122116 Firefox/3.0.17
Accept image/png,image/*;q=0.8,*/*;q=0.5
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost/kincumberunitingchurch/index.php?sid=tgl9jq3f71nau3cj9vps6pna03
Cookie sid=tgl9jq3f71nau3cj9vps6pna03; PHPSESSID=m0jvven6d7l65pl6odm9ecfnt4
If-None-Match b98e0795b509be20146f58e06fbb624f
Cache-Control max-age=0
for other files the sever sends first:
(Status-Line) HTTP/1.1 200 OK
Date Thu, 21 Jan 2010 08:55:25 GMT
Server Apache/2.2.11 (Win32) PHP/5.2.9-1
Last-Modified Wed, 30 Dec 2009 02:40:58 GMT
Etag "1000000013d35-40d9-47be9117f6280"
Accept-Ranges bytes
Content-Length 16601
Keep-Alive timeout=5, max=84
Connection Keep-Alive
Content-Type image/png
and my browser send the following on the next request:
(Request-Line) GET /kincumberunitingchurch/img/cbuttons.png HTTP/1.1
Host localhost
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.0.17) Gecko/2009122116 Firefox/3.0.17
Accept image/png,image/*;q=0.8,*/*;q=0.5
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost/kincumberunitingchurch/mystyle.css
Cookie sid=tgl9jq3f71nau3cj9vps6pna03; PHPSESSID=m0jvven6d7l65pl6odm9ecfnt4
If-Modified-Since Wed, 30 Dec 2009 02:40:58 GMT
If-None-Match "1000000013d35-40d9-47be9117f6280"
Cache-Control max-age=0
why would it send the If-Modified-Since header
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评论（2）
您的第一个发送的标头显示为“Last-Modfied”，这是一个拼写错误（Modified 中的第一个“i”丢失了）。
Your first sended header reads "Last-Modfied", which is a typo (the first 'i' in Modified is missing).
你能看看第一个示例中的 Last-Modfied 是否不是服务器端的拼写错误
can you look if the Last-Modfied inside the first example isn't a typo at the server side