我的HTTP条件实现是否可以在PHP中获得答案？ [英] Is my implementation of HTTP Conditional Get answers in PHP is OK?

问题描述

经过大量搜索，阅读我找到的每一个教程并在这里提出一些问题，我终于成功地回答了（至少我认为）if-none-match和if-modified-自HTTP请求以来。

为了快速回顾一下，我在每个页面可缓存的内容上都是这样做的：

  session_cache_limiter（ '公共'）; //缓存客户端和代理
 session_cache_expire（180）; // 3小时
 header（'Content-Type：'。$ documentMimeType。'; charset ='。$ charset）; 
 header（'ETag：''。$ eTag。''）; // $ eTag是$ currentLanguage + $ lastModified 
的MD5如果（$ isXML）
 header（'Vary：Accept'）; // $ documentMimeType可以是XHTML的application / xhtml + xml或text / html（基于$ _SERVER ['HTTP_ACCEPT']）
 header（'Last-Modified：'。$ lastModified）; 
 header（'Content-Language：'。$ currentLanguage）; 
  

另外，每个页面都有自己的URL（适用于各种语言）。例如，index.php将以英文的URL/ en / home和法文的/ fr / accueil提供。 我的大问题是从HTTP请求仅在需要时回答304未修改以if-none-match和if-modified。

doc我发现是：
http://rithiur.anthd.com/tutorials /conditionalget.php

这就是我所做的实现（这段代码在可缓存的页面上称为ASAP）： p>

  $ ifNoneMatch = array_key_exists（'HTTP_IF_NONE_MATCH'，$ _SERVER）？ $ _SERVER ['HTTP_IF_NONE_MATCH']：false; 
 $ ifModifiedSince = array_key_exists（'HTTP_IF_MODIFIED_SINCE'，$ _SERVER）？ $ _SERVER ['HTTP_IF_MODIFIED_SINCE']：false; 
 
 if（$ ifNoneMatch！== false&& $ ifModifiedSince！== false）
 {
 // if if-none-match and if-modified-since已收到。 
 //它们必须匹配文档值才能发送HTTP 304答案。 
 if（$ ifNoneMatch == $ eTag&& $ ifModifiedSince == $ lastModified）
 {
 header（'Not Modified'，true，304）; 
 exit（）; 
} 
} 
 else 
 {
 //只收到一个头，它与文档值匹配，发送一个HTTP 304答案。 
 if（（$ ifNoneMatch！== false& $ amp; $ ifNoneMatch == $ eTag）||（$ ifModifiedSince！== false&& $ ifModifiedSince == $ lastModified））
 { 
 header（'Not Modified'，true，304）; 
 exit（）; 
 
 
  

我的问题有两个：

• 这是否是正确的方法？我的意思是，当if-none-match和if-modified-since发送时，两者必须匹配以回答304，并且如果只发送两个中的一个，则只匹配此发送即可发送一个304？


• 当在这里描述的上下文中使用时，这2个片段是否是公共缓存友好的（我的意思是缓存对代理和 Web浏览器友好） / li>
  

顺便说一句，我只使用PHP 5.1.0+（我不支持低于此值的版本）。

编辑：增加赏金...我期待高质量的答案。如果您在猜测某事，请不要回答/投票！ 这不完全正确。请查看算法： alt text http://img532.imageshack.us/img532 /1017/cache.png

解决方案代理友好，您可以使用Cache-control：proxy-revalidate来强制缓存服从您提供的任何新鲜度信息资源（仅适用于共享代理缓存）

以下是可能有所帮助的功能：

$

 函数isModified（$ mtime，$ etag）{
 return！（（
 isset（$ _ SERVER ['HTTP_IF_MODIFIED_SINCE']）
&& 
 strtotime（$ _ SERVER ['HTTP_IF_MODIFIED_SINCE']）> = $ mtime 
）||（
 isset（$ _ SERVER ['HTTP_IF_NONE_MATCH']）
&& 
 $ _SERVER ['HTTP_IF_NONE_MATCH'] == $ etag 
））; 
} 
  

我建议你看看下面的文章： http://www.peej.co.uk/articles/http-caching.html

更新： AlexV] 甚至有可能在同一时间收到if-none-match和if-modified-

你绝对可以同时设置。但是：

lockquote

如果实体标签都不匹配，那么服务器可以执行请求的方法，就好像If-None-Match头字段不存在，但也必须忽略请求中的任何If-Modified-Since头字段。也就是说，如果没有实体标签匹配，那么服务器绝不会返回304（未修改）响应。

RFC2616＃14.26

示例值（W代表'weak';详细信息请参阅 RFC2616＃13.3.3 ）：

  If-None-Match：xyzzy，r2d2xxxx， c3piozzzz
 If-None-Match：W /xyzzy，W /r2d2xxxx，W /c3piozzzz
 If-Modified-Since：Sat，29 Oct 1994 19:43:31 GMT 
 If-None-Match：* 
  

特殊情况下，值* 匹配资源的任何当前实体。

After searching a lot, reading every tutorials I've found and asking some questions here, I've finally managed to answer corrctly (at least I think) to if-none-match and if-modified-since HTTP requests.

To do a quick recap, this is what I do on every pages cacheable:

session_cache_limiter('public'); //Cache on clients and proxies
session_cache_expire(180); //3 hours
header('Content-Type: ' . $documentMimeType . '; charset=' . $charset);
header('ETag: "' . $eTag . '"'); //$eTag is a MD5 of $currentLanguage + $lastModified
if ($isXML)
    header('Vary: Accept'); //$documentMimeType can be either application/xhtml+xml or text/html for XHTML (based on $_SERVER['HTTP_ACCEPT'])
header('Last-Modified: ' . $lastModified);
header('Content-Language: ' . $currentLanguage);

Also, every page have it's own URL (for every languages). For example, "index.php" will be served under URL "/en/home" in English and "/fr/accueil" in French.

My big problem was to answer a "304 Not Modified" to if-none-match and if-modified-since HTTP requests only when needed.

The best doc I've found is: http://rithiur.anthd.com/tutorials/conditionalget.php

And this is the implementation I did of it (this piece of code is called ASAP on pages that can be cached):

$ifNoneMatch = array_key_exists('HTTP_IF_NONE_MATCH', $_SERVER) ? $_SERVER['HTTP_IF_NONE_MATCH'] : false;
$ifModifiedSince = array_key_exists('HTTP_IF_MODIFIED_SINCE', $_SERVER) ? $_SERVER['HTTP_IF_MODIFIED_SINCE'] : false;

if ($ifNoneMatch !== false && $ifModifiedSince !== false)
{
    //Both if-none-match and if-modified-since were received.
    //They must match the document values in order to send a HTTP 304 answer.
    if ($ifNoneMatch == $eTag && $ifModifiedSince == $lastModified)
    {
        header('Not Modified', true, 304);
        exit();
    }
}
else
{
    //Only one header received, it it match the document value, send a HTTP 304 answer.
    if (($ifNoneMatch !== false && $ifNoneMatch == $eTag) || ($ifModifiedSince !== false && $ifModifiedSince == $lastModified))
    {
        header('Not Modified', true, 304);
        exit();
    }
}

My question is two fold:

• Is it the correct way to do it? I mean when if-none-match and if-modified-since are sent, both must match to answer a 304, and if only one of the two is sent, only matching this one is OK to send a 304?
• When used in the context described here, is these 2 snippets are public cache friendly (I mean cache friendly on proxies and Web browsers)?

BTW, I use PHP 5.1.0+ only (I don't support versions lower that that).

Edit: Added bounty... I expect quality answer. Don't answer/vote if you are guessing something!

解决方案

• It's not quite correct. Please take a look at the algorithm: alt text http://img532.imageshack.us/img532/1017/cache.png
• The solution is proxy-friendly, you may use Cache-control: proxy-revalidate to force caches to obey any freshness information you give them about a resource (only applies to shared|proxy caches)

Here is the function that might help:

function isModified($mtime, $etag) {
    return !( (
        isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])
        && 
        strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $mtime
    ) || (
        isset($_SERVER['HTTP_IF_NONE_MATCH'])
        && 
        $_SERVER['HTTP_IF_NONE_MATCH'] == $etag
    ) ) ;
}

I suggest that you take a look at the following article: http://www.peej.co.uk/articles/http-caching.html

Update:

[AlexV] Is is even possible to receive if-none-match AND if-modified-since at the same time?

You can definitely have both set. However:

If none of the entity tags match, then the server MAY perform the requested method as if the If-None-Match header field did not exist, but MUST also ignore any If-Modified-Since header field(s) in the request. That is, if no entity tags match, then the server MUST NOT return a 304 (Not Modified) response.

RFC2616 #14.26

Example values (W stands for 'weak'; read more in RFC2616 #13.3.3):

If-None-Match: "xyzzy", "r2d2xxxx", "c3piozzzz"
If-None-Match: W/"xyzzy", W/"r2d2xxxx", W/"c3piozzzz"
If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
If-None-Match: *

As a special case, the value "*" matches any current entity of the resource.

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