A brief analysis of HTTP message header web page cache control and introduction to common header instructions_PHP tutorial

The cache of web pages is controlled by the "Cache-control" in the HTTP message header. Common values ​​include private, no-cache, max-age, must-revalidate, etc. The default is private. Its function is divided into the following situations according to different re-browsing methods:
(1) Open a new window
The value is private, no-cache, must-revalidate, then open a new window to visit The server will be accessed again every time.
If a max-age value is specified, the server will not be accessed again within this value, for example:
Cache-control: max-age=5 (indicates 5 seconds after accessing this web page) Accessing again within seconds will not go to the server)
(2) Press Enter in the address bar
if the value is private or must-revalidate, the server will be accessed only the first time, and will not be accessed in the future. Visit again.
The value is no-cache, then it will be accessed every time.
If the value is max-age, it will not be accessed again before expiration.
(3) Press the back button
If the value of is private, must-revalidate, max-age, it will not be accessed again. If the value of
is no-cache, it will be accessed every time. Repeated visits
(4) Press the refresh button
No matter what the value is, it will be visited repeatedly
When the Cache-control value is "no-cache", accessing this page will not be on the Internet Temporary article folder leaves page backup.
In addition, caching can also be affected by specifying the "Expires" value. For example, if the Expires value is specified as a time that has long passed, then if you press Enter repeatedly in the address bar when accessing this network, the access will be repeated each time: Expires: Fri, 31 Dec 1999 16:00:00 GMT
For example : Disable page caching in IE
http response message header setting:
CacheControl = no-cache
Pragma=no-cache
Expires = -1
Expires is a good thing. If the web pages on the server change frequently, set it to -1 to indicate immediate expiration. If a web page is updated at 1 am every day, you can set Expires to 1 am the next day.
When the HTTP1.1 server specifies CacheControl = no-cache, the browser will not cache the web page.
Legacy HTTP 1.0 servers cannot use the Cache-Control header.
So in order to be backward compatible with HTTP 1.0 servers, IE provides special support for HTTP using the Pragma:no-cache header.
If the client communicates with the server over a secure connection (https://)/ and the server returns the Pragma:no-cache header in the response,
Internet Explorer will not cache the response. Note: Pragma:no-cache only prevents caching when used in a secure connection. If used in a non-secure page, the handling is the same as Expires:-1. The page will be cached but marked as expired immediately.

Header common commands
The header is divided into three parts:
The first part is the version of the HTTP protocol (HTTP-Version);
The second part is the status code (Status);
The third part is the reason phrase (Reason-Phrase).

Copy code The code is as follows:

// fix 404 pages: Use this header command to solve the 404 header caused by URL rewriting
header('HTTP/1.1 200 OK');

// set 404 header : Page not found
header('HTTP/1.1 404 Not Found');

//Page permanent redirection, you can tell search engines to update their urls
// set Moved Permanently header ( good for restrictions)
// use with location header
header('HTTP/1.1 301 Moved Permanently');

// Access restricted
header('HTTP/1.1 403 Forbidden ');

// Server error
header('HTTP/1.1 500 Internal Server Error');

// Redirect to a new location
// redirect to a new location:
header('Location: http://www.www.jb51.net);

Redirect after a period of delay
// redirect with delay:
header('Refresh: 10; url=http://www.jb51.net');
print 'You will be redirected in 10 seconds';

// Override X-Powered-By value
// override X-Powered-By: PHP:
header('X-Powered-By: PHP/4.4.0');
header('X-Powered-By: Brain/0.6b ');

// content language (en = English)
// content language (en = English)
header('Content-language: en');

//Last modified time (can be used when caching)
// last modified (good for caching)
$time = time() - 60; // or filemtime($fn), etc
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $time).' GMT');

// Tell the browser that the content to be obtained has not been updated yet
// header for telling the browser that the content
// did not get changed
header('HTTP/1.1 304 Not Modified');

// set the length of the content ( Can be used when caching):
// set content length (good for caching):
header('Content-Length: 1234');

// Used to download files:
// Headers for an download:
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="example.zip"');
header('Content-Transfer-Encoding: binary');

// Disable caching of the current document:
// load the file to send:readfile('example.zip');
// Disable caching of the current document:
header('Cache-Control: no-cache, no-store, max-age=0, must-revalidate');
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');

// Set content type:
// Date in the pastheader('Pragma: no-cache');
// set content type:
header('Content-Type: text/html; charset=iso-8859-1');
header('Content-Type: text/html; charset=utf-8');
// plain text file
header('Content-Type: text/plain');

// JPG picture
header('Content-Type: image/jpeg');

// ZIP file
header('Content-Type: application/zip');

// PDF file
header('Content-Type: application/pdf');

// Audio MPEG (MP3,...) file
header('Content-Type: audio/mpeg');

// Flash animation// show sign in box
header('Content-Type: application/x-shockwave-flash');

// Display the login dialog box, which can be used for HTTP authentication
header('HTTP/1.1 401 Unauthorized ');
header('WWW-Authenticate: Basic realm="Top Secret"');
print 'Text that will be displayed if the user hits cancel or ';
print 'enters wrong login data ';

http://www.bkjia.com/PHPjc/327939.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/327939.htmlTechArticleThe cache of web pages is controlled by the "Cache-control" in the HTTP message header. Common values ​​​​are: private, no-cache, max-age, must-revalidate, etc., the default is private. Its functions vary depending on...