HTTP header information explained and set

Explanation of header information in HTTP messages This article follows: The HTTP message includes the client's request message to the server and the server's response message to the client. These two types of messages consist of a starting line, one or more header fields, a blank line that is just the end of the head field, and an optional message body. The header fields of HTTP include the general header, the request header, the response header, and the four parts of the entity header. Each header field consists of a domain name, a colon (:), and a domain value of three parts

header information for HTTP request

1. HTTP request Mode

As the following table:

GET	Request a file from a Web server
POST	Send data to the Web server for processing by the Web server
PUT	Send data to the Web server and store it inside the Web server
HEAD	Checks if an object exists
DELETE	Delete a file from the Web server
CONNECT	Providing support for channels
TRACE	Trace the path to the server
OPTIONS	Querying the performance of a Web server

Description:

Mainly used to "get" and "POST".

Example:

POST/TEST/TUPIAN/CM http/1.1

into three parts:

(1) Post:http request method

(2)/TEST/TUPIAN/CM: Request the Directory address (or directive) of the Web server

(3) Http/1.1:uri (Uniform Resource Identifier, Uniform Resource Identifier) and its version

remark:

In Ajax, the corresponding method property is set.

2. Host

Description

The requested Web server domain name address

3, User-agent

Description

Details of the browser type that the HTTP client is running. With this header information, the Web server can determine the client browser category to the current HTTP request.

Instance:

user-agent:mozilla/5.0 (Windows; U Windows NT 5.1; ZH-CN; rv:1.8.1.11) gecko/20071127 firefox/2.0.0.11

4. Accept

Description

Specifies the types of content that clients can receive, and the order in which they are received in the content type indicates the order in which clients receive them.

For example:

accept:text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5

remark:

In the AJAX Code encapsulation of Prototyp (1.5), the accept default is set to "Text/javascript, text/html, Application/xml, Text/xml, */*". This is because Ajax obtains the JSON data pattern returned by the server by default.

In AJAX code, you can use the setRequestHeader function method in the XMLHttpRequest object to dynamically set these header information.

5, Accept-language

Description

Specifies the preferred language for the HTTP client browser to display the return information.

Instance:

accept-language:zh-cn,zh;q=0.5

This defaults to Chinese.

6, Accept-encoding

Description

Specifies that the Web server that the client browser can support returns the content compression encoding type. Indicates that the server is allowed to compress the output before it is sent to the client to conserve bandwidth. The return compression format that the client browser can support is set here.

Instance:

Accept-encoding:gzip,deflate

Note:

In fact, in many of Baidu's product lines, Apache compresses the data in gzip format before returning the page data to the client.

7, Accept-charset

Description

The set of character encodings that the browser can accept.

Instance:

accept-charset:gb2312,utf-8;q=0.7,*;q=0.7

8, Content-type

Description

Displays the content type submitted by this HTTP request. This property is typically only required for post submission.

Instance:

Content-type:application/x-www-form-urlencoded;charset:utf-8

There are two types of encoding available for the Content-type property values:

(1) "application/x-www-form-urlencoded": the type of encoding used when the form data is submitted to the server, the default value is "application/x-www-form-urlencoded". However, this encoding is inefficient when sending large amounts of text to the server, including text or binary data that contains non-ASCII characters.

(2) "Multipart/form-data": When the file is uploaded, the type of encoding used should be "Multipart/form-data", which can both send text data and support binary data upload.

You can use "application/x-www-form-urlencoded" when committing to data alone, and when you commit a file, you need to use the "multipart/form-data" encoding type.

The charset character encoding of the commit content is also specified in the Content-type property. Typically not set, it simply tells the Web server what character encoding to use for the data submitted by the post.

Generally in the development process, the front end works with the backend UI engineer to discuss what character encoding format to use for post submission, and then the backend UI engineer to parse the submitted data according to a fixed character encoding. So the charset set here does not have much effect.

9, Connection

Description

Indicates whether a persistent connection is required. If the Web server side sees the value here as "keep-alive", or sees the request using an HTTP 1.1 (HTTP 1.1 By default for persistent connection), it can take advantage of the persistent connection, when the page contains multiple elements (such as applets, pictures), Significantly reduce the time it takes to download. To do this, the Web server needs to send a content-length (the length of the message body) header back to the client HTTP header, and the simplest implementation is to write the content to Bytearrayoutputstream first, and then Calculates the size of the content before it is formally written.

Instance:

connection:keep-alive

10, Keep-alive

Description

Displays the keep-alive time for this HTTP connection. The client-to-server connection continues to be valid, and the Keep-alive feature avoids establishing or re-establishing a connection when a subsequent request to the server occurs.

The previous HTTP request is a one-stop connection, and after the http/1.1 protocol, there is a long connection, that is, the connection is not broken within the specified keep-alive time.

Instance:

keep-alive:300

11. Cookies

Description

When an HTTP request is sent, all cookie values stored under that request domain are sent to the Web server.

12, Referer

Description

contains a URL where the user accesses the currently requested page from the page represented by the URL Responses Part

Header	explain	Example
Accept-ranges	Indicates whether the server supports the specified range request and what kind of staging request	Accept-ranges:bytes
Age	Estimated time (in seconds, non-negative) from the original server to the proxy cache	Age:12
Allow	A valid request behavior for a network resource is not allowed to return 405	Allow:get, HEAD
Cache-control	Tell if all caching mechanisms can be cached and which type	Cache-control:no-cache
Content-encoding	The type of return content compression encoding supported by the Web server.	Content-encoding:gzip
Content-language	The language of the response body	Content-language:en,zh
Content-length	The length of the response body	content-length:348
Content-location	Alternate alternative address to request resource substitution	Content-location:/index.htm
Content-md5	Returns the MD5 checksum value of a resource	content-md5:q2hly2sgsw50zwdyaxr5iq==
Content-range	The byte position of this section in the entire return body	Content-range:bytes 21010-47021/47022
Content-type	Returns the MIME type of the content	content-type:text/html; Charset=utf-8
Date	Time the original server message was issued	Date:tue, 08:12:31 GMT
ETag	The current value of the entity label of the request variable	ETag: "737060cd8c284d8af7ad3082f209582d"
Expires	Date and time when the response expires	Expires:thu, 16:00:00 GMT
Last-modified	Requested last modified time for resource	Last-modified:tue, 12:45:26 GMT
Location	Used to redirect the receiver to the location of the non-request URL to complete the request or identify the new resource	Location:http://www.zcmhi.com/archives/94.html
Pragma	Includes implementing a specific instruction that can be applied to any receiver on the response chain	Pragma:no-cache
Proxy-authenticate	It indicates the authentication scheme and the parameters on the URL that can be applied to the proxy	Proxy-authenticate:basic
Refresh	Applied to redirect or a new resource was created, redirected after 5 seconds (proposed by Netscape, supported by most browsers)	Refresh:5; Url= http://www.zcmhi.com/archives/94.html
Retry-after	Notifies the client to try again after a specified time if the entity is temporarily undesirable	retry-after:120
Server	Web Server Software Name	server:apache/1.3.27 (Unix) (Red-hat/linux)
Set-cookie	Set HTTP Cookies	Set-cookie:userid=johndoe; max-age=3600; Version=1
Trailer	Indicates that the header domain is present at the end of the chunked transfer code	Trailer:max-forwards
Transfer-encoding	File transfer encoding	Transfer-encoding:chunked
Vary	Tells the downstream agent whether to use the cache response or request from the original server	Vary: *
Via	Tells the proxy client where the response was sent by	via:1.0 Fred, 1.1 nowhere.com (apache/1.1)
Warning	Warning about possible issues with the entity	warning:199 Miscellaneous Warning
Www-authenticate	Indicates the authorization scheme that the client request entity should use	Www-authenticate:basic

second, the header of the setting method

Xhr.setresponseheader ("Content-type", "application/x-www-form-urlencoded");//Set Request header

PHP gets the post parameters in several ways

1, $_post[' paramname '] can only receive data submitted by content-type:application/x-www-form-urlencoded

2, file_get_contents ("Php://input") for most types of content-type

Php://input allows the raw data to be read from the POST. Compared to $HTTP _raw_post_data, it brings less pressure to memory and does not require any special php.ini settings. Php://input cannot be used for enctype= "Multipart/form-data".

3, globals[' http_raw_post_data '];  always produce   globals[' Http_raw_post_data '];  always produces   globals[' Http_raw_post_data ']; Always produce http_raw_post_data variables containing the original POST data. This variable is only generated when it encounters data that does not recognize the MIME type. $HTTP _raw_post_data is not available for enctype= ' multipart/form-data ' form data.

If the POST data is not recognized by PHP, you can use $GLOBALS [' Http_raw_post_data '] to receive it, such as text/xml or soap, and so on.