Use of the PHP header function
The cache of the Web page is controlled by the "Cache-control" in the HTTP message header, and the common values are private, No-cache, Max-age, must-revalidate, etc., and the default is private. Its function is divided into the following situations according to different ways of re-browsing:
(1) Open a new window
?The value is private, No-cache, Must-revalidate, and the server is re-accessed when a new window is opened.
If you specify a max-age value, the server is not re-accessed in the time within this value, for example:
Cache-control:max-age=5 (indicates that access will not go to the server within 5 seconds of accessing this page)
(2) Enter in the Address bar
?The value is private or must-revalidate the server is accessed only on the first visit and is no longer accessed at a later time.
?The value is No-cache, which is accessed every time.
?The value of max-age is not repeated until it expires.
(3) Press Back button
?? The value is private, must-revalidate, Max-age, and is not re-accessed.
?? A value of No-cache, which is repeatedly accessed every time
(4) Press the Refresh button
No matter what the value, it will be accessed repeatedly
When the Cache-control value is "No-cache", accessing this page does not leave a page backup in the Temporary Internet Article folder.
Also, the cache is affected by specifying a value of "Expires". For example, specifying the Expires value is a time long past, then when you visit this network repeatedly press ENTER in the Address bar, then each time will be repeated access: Expires:fri, Dec 1999 16:00:00 GMT
For example: Prevent pages from being cached in IE
HTTP response message Header settings:
CacheControl = No-cache
Pragma=no-cache
Expires =-1
Expires is a good thing, if the Web page on the server changes frequently, it is set to 1, indicating immediate expiration. If a webpage is updated daily 1 o'clock in the morning, you can set expires to 1 o'clock in the morning the next day.
When the HTTP1.1 server specifies CacheControl = No-cache, the browser does not cache the page.
Legacy HTTP 1.0 Servers cannot use the Cache-control header.
So for backwards compatibility with HTTP 1.0 servers, IE uses the Pragma:no-cache header to provide special support for HTTP.
If the client communicates with the server through a secure connection (https://), and the server returns the Pragma:no-cache header in the response,
Internet Explorer does not cache this response. Note: Pragma:no-cache prevents caching only when used in a secure connection, and if used in a non-secure page, is processed in the same way as expires:-1, the page is cached but is marked for immediate expiration
Header Common Directives
The header is divided into three parts:
The first part is the version of the HTTP Protocol (http-version);
The second part is state code (status);
The third part is the reason phrase (reason-phrase).
Fix 404 Pages:? Use this header command to resolve the 404 header generated by the URL rewrite?
Header (' http/1.1 OK ');??
??
Set 404 header:? Page Not found
Header (' http/1.1 404 Not Found ');??
??
Pages are permanently deleted and can tell the search engine to update their URLs
Set Moved permanently header (good for redrictions)??
Use with the location header??
Header (' http/1.1 301 Moved permanently ');?
Restricted access
Header (' http/1.1 403 Forbidden ');
Server error
Header (' http/1.1 Internal Server Error ');
??
Redirect to a new location
Redirect to a new location:??
Header (' location:http://www.sina.com.cn);??
??
Redirect after a period of delay
Redrict with delay:??
Header (' refresh:10; url=http://www.sina.com.cn ');??
print ' You'll be redirected in ten seconds ';??
??
Overwrite 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 = 中文版)
Content language (en = 中文版)??
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 what to get is not updated
Header for telling the browser 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 ');??
??
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, Jul 1997 05:00:00 GMT ');??
To set the 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 ');??
Header (' Content-type:text/plain ');??
??
Plain text file??
Header (' Content-type:image/jpeg ');??
??
JPG picture??
Header (' Content-type:application/zip ');??
??
ZIP file??
Header (' content-type:application/pdf ');??
??
PDF file??
Header (' Content-type:audio/mpeg ');??
??
Audio MPEG (MP3,...) file??
Header (' Content-type:application/x-shockwave-flash ');??
??
Displays the Login dialog box, which can be used for HTTP authentication
Flash animation//show sign in box??
Header (' http/1.1 401 Unauthorized ');??
Header (' Www-authenticate:basic realm= ' Top Secret ');??
print ' Text that'll be displayed if the user hits Cancel or ';??
print ' enters wrong login data ';? >
