PHP Header Cache-header parameter jutting

PHP Header Cache---header parameter description

1. Accept: Tell the Web server what type of media you accept, */* represents any type, type/* represents all subtypes under that type, Type/sub-type.

2. Accept-charset:?? The browser affirms the character set it receives
Accept-encoding: The browser declares itself to receive the encoding method, usually specifies the compression method, whether compression is supported, what compression method is supported (Gzip,deflate)
Accept-language:: Browser affirms the language you receive
The difference between language and character set: Chinese is language, Chinese has many character sets, such as BIG5,GB2312,GBK and so on.

3. The Accept-ranges:web server indicates whether it accepts requests to obtain a portion of its entity, such as a portion of a file.
Bytes: Accept, none: Indicates not accepted.

4. Age: When the proxy server responds to a request with its own cached entity, the header is used to indicate how long the entity has been from the time it was produced to the present.

5. Authorization: When the client receives a www-authenticate response from the Web server, it uses that header to respond to its own authentication information to the Web server.

6. Cache-control: Request: No-cache (do not cache the entity, request now from the Web server to fetch)
Max-age: (Accept only the age value is less than the Max-age value, and there are no expired objects)
Max-stale: (Can accept past objects, but the expiration time must be less than Max-stale value)
Min-fresh: (accepts cached objects whose freshness life is greater than the sum of its current age and Min-fresh values)
Response: Public (can respond to any user with Cached content)
Private (only cached content can be used to respond to the user who previously requested the content)
No-cache (can be cached, but only after the Web server has verified that it is valid to be returned to the client)
Max-age: (The expiration time of the object contained in this response)
All:no-store (cache not allowed)

7. Connection: Request: Close (Tell the Web server or proxy server, after completing the response of this request, disconnect, do not wait for subsequent requests for this connection).
KeepAlive (tells the Web server or proxy server, after completing the response of this request, remains connected, waiting for subsequent requests for this connection).
Response: Close (the connection is closed).
KeepAlive (connection is maintained, waiting for subsequent requests for this connection).
Keep-alive: If the browser requests to remain connected, the header indicates how long (in seconds) you want the WEB server to remain connected.
Example: keep-alive:300

8. The Content-encoding:web server indicates what compression method (Gzip,deflate) It uses to compress the objects in the response.
Example: Content-encoding:gzip??????????????????
The Content-language:web server tells the browser the language of the object it responds to.

The Content-length:web server tells the browser the length of the object it responds to.
Example: content-length:26012
Content-range:?? The WEB server indicates which part of the object The response contains is part of the whole.
Example: Content-range:bytes 21010-47021/47022
Content-type:??? The WEB server tells the browser what type of object it responds to.
Example: Content-type:application/xml

9. ETag: is an object (such as a URL) of the flag value, in terms of an object, such as an HTML file, if modified, its ETag will not be modified,
Therefore, the role of the ETAG is similar to the role of last-modified, mainly for the WEB server to determine whether an object has changed.
For example, when a previous request for an HTML file, the ETag was obtained, and when the file is requested this time, the browser will send the previously obtained ETag value sent to
Web server, and the Web server compares the ETag to the current etag of the file, and then knows that the file has not changed.

The Expired:web server indicates when the entity will expire and, for expired objects, can be used to respond to customer requests only after it has verified its validity with the Web server.
It's http/1.0 's head.
Example: Expires:sat, 10:02:12 GMT

Host: The client specifies the domain/IP address and port number of the Web server that you want to access.
Example: Host:rss.ifeng.com

If-match: If the ETag of an object does not change, it actually means that the object has not changed before the requested action is executed.
If-none-match: If the ETag of an object changes, it also means that the object has changed to perform the requested action.

If-modified-since: If the requested object is modified after the specified time in the header, the requested action (such as the return object) is executed, otherwise the code 304 is returned, telling the browser that the object has not been modified.
Example: If-modified-since:thu, APR 09:14:42 GMT
If-unmodified-since: The requested action (such as returning an object) is performed if the requested object has not been modified after the specified time in the header.

If-range: The browser tells the WEB server that if the object I requested doesn't change, give me the missing part, and if the object changes, give me the whole object.
The browser can tell the WEB server whether the object has changed by sending the ETag of the requested object or the last modification time it knows.
Always used with the Range header.

Last-modified:web server considers the last modification time of the object, such as the last modification time of the file, the last generation time of the dynamic page, and so on.
For example: Last-modified:tue, May 02:42:43 GMT

The Location:web server tells the browser that the object you are trying to access has been moved to a different location to fetch it at the location specified by the header.
For example: Location:

PRAMGA: The main use of pramga:no-cache, equivalent to Cache-control:no-cache.
Example: Pragma:no-cache

Proxy-authenticate: The proxy server responds to the browser and requires it to provide proxy authentication information.
Proxy-authorization: The browser responds to the proxy server's authentication request and provides its own identity information.

Range: A browser (such as a Flashget multi-threaded download) tells the WEB server what part of the object you want to take.
Example: range:bytes=1173546-

Referer: The browser indicates to the Web server from which page/url obtained/clicked the URL/url in the current request.
Example: referer:http://www.ifeng.com/

The Server:web server indicates what software and version information it is.
Example: server:apache/2.0.61 (Unix)

User-agent: The browser indicates its identity (which browser).
For example: user-agent:mozilla/5.0 (Windows; U Windows NT 5.1; ZH-CN; rv:1.8.1.14) gecko/20080404 firefox/2.0.0.14

The Transfer-encoding:web server indicates how it encodes the response message body (not the object inside the message body), such as whether it is chunked (chunked).
Example: transfer-encoding:chunked

The Vary:web server uses the contents of the header to tell the Cache server under what conditions the object returned by this response responds to subsequent requests.
If the source Web server receives the first request message, the header of its response message is: Content-encoding:gzip; Vary:content-encoding
The Cache server then parses the header of the subsequent request message and checks its accept-encoding to see if it is consistent with the Vary header value of the previous response, that is, whether to use
The same content encoding method, which prevents the cache server from responding to a browser that does not have the ability to decompress with the compressed entity inside its cache.
Example: vary:accept-encoding

Via: Lists which proxy servers The response from the client to OCS or in the opposite direction passed, and what protocol (and version) they were using to send the request.
When a client request arrives at the first proxy server, the server adds the Via header to its own request and fills in its own information when the next proxy server
When a request for the first proxy server is received, it copies the requested via header of the previous proxy server in its own request and adds the relevant information to the back,
And so on, when OCS receives a request from the last proxy server, it checks the Via header to know which route the request is routed through.

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