blocks|key|622547|text|其背后的主要动机是在HTTP1.1中重用现有的TCP连接。Content-Length可以为接收者划分响应结束的位置。至于其他头部，比如指定MIME类型的Content-Type，它们是针对接收者的，这样她就可以根据内容的类型知道如何处理结果。例如，在火狐中，你可以指定对不同的MIME类型执行什么操作。如果你能弹出浏览器的保存对话框或者用application/pdf的Content-Type在查看器中打开PDF|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|622548|entityMap^0|T|E|25|C|4Q|F|56|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

The main motivation behind it is re-using an existing TCP connection in HTTP 1.1. <code>Content-Length</code> can demarcate where the response ends for the recipient. 
As for the other headers, like <code>Content-Type</code> which specifies the MIME-type, they are for the recipient so that she would know what to do with the result depending on the type of the content
For example, in Firefox you can specify what action to perform with different MIME-types. If you can pop-up the browser's save dialog or open a PDF in viewer with <code>Content-Type</code> of <code>application/pdf</code>

blocks|key|407576|text|在涉及content-type:+text/html的地方，它主要是告诉客户端期望什么，以及通常如何处理文件。在机器人的情况下，它可以用于搜索引擎优化的目的，因为它告诉机器人它正在查看什么类型的文件，这可以改变它的解析/排名方式。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|407577|在使用content-length的情况下，它只是让客户端知道预期的文件有多大，从而知道响应的结束位置。|407578|entityMap^0|3|N|0|3|E|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

Where <code>content-type: text/html</code> is concerned, it's mainly to tell the client what to expect and usually how to handle the file. In the case of bots, it can be useful for SEO purposes as it tells the bot what type of file it's looking at which can change how it's parsed/ranked.

In the case of <code>content-length</code>, it's just to let the client know how large a file to expect and thus where the response ends.

blocks|key|622807|text|获取远程文件大小的最佳方法(对我有效)是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|622808|$head+=+array_change_key_case(get_headers($file,+TRUE));
$filesize+=+$head['content-length'];|code-block|syntax|javascript|622809|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The best way (that is working for me) of getting size of a remote file:

<pre><code>$head = array_change_key_case(get_headers($file, TRUE));
$filesize = $head['content-length'];
</code></pre>

blocks|key|622845|text|设置content-length的一个很好的用法是当您希望将响应发送到客户端时，即使之后您仍然希望执行更多耗时的操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|622846|请参阅this+answer，它解释了您已经设置了内容长度，编写了输出，然后可以在脚本中执行进一步的操作，而不会让客户端等待更长时间。|offset|length|622847|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/6963519/43615^0|0|3|B|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

One supposedly good use for setting the content-length is when you like to send your response to the client even though you still like to perform more time-consuming operations afterwards.

See <a href="https://stackoverflow.com/a/6963519/43615">this answer</a> that explains that you'd set the content length, write your output and then can perform further operations in your script without making the client wait any longer.

blocks|key|408276|text|变化|type|unstyled|depth|inlineStyleRanges|entityRanges|data|408277|$content+=+ob_get_contents();|code-block|syntax|javascript|408278|至|408279|$content+=+ob_get_clean();|408280|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Change
<pre><code>$content = ob_get_contents();
</code></pre>
to
<pre><code>$content = ob_get_clean();
</code></pre>

Does it give me any advantage if I set this header when generating normal HTML pages?

I see that some frameworks out there will set this header property and I was wondering why...
(Along with other headers, like <code>Content-Type: text/html</code>)

Does browser load the site faster or smoother?

ps: they do it like:

<pre><code>ob_start();

... stuff here...

$content = ob_get_contents();
$length = strlen($content);

header('Content-Length: '.$length);

echo $content;
</code></pre>

Content-length and other HTTP headers?

如果我在生成普通的HTML页面时设置这个页眉，会给我带来什么好处吗？我看到一些框架会设置这个头属性，我想知道为什么……(以及其他标头，如Content-Type: text/html)浏览器加载站点的速度更快还是更流畅？ps:他们是这样做的：ob_start();... stuff here...$content = ...

问Content-length和其他HTTP报头？
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