Detailed explanation of php header usage

Header("Location: http://www.php.net");
?>

to force users to get the latest every time they visit this page data instead of using the cache that exists on the client side.

//Tell the browser the expiration time of this page (expressed in Greenwich Mean Time), as long as it is a date that has passed.
header("Expires: Mon, 26 Jul 1970 05:00:00 GMT");
//Tell the browser the last updated date of this page (expressed in Greenwich Mean Time), which is the same day, the purpose is to force the browser to obtain The latest information
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . "GMT");
//Tell the client browser not to use cache
header("Cache-Control: no-cache, must-revalidate");
//Parameters (compatible with previous servers), that is, compatible with the HTTP1.0 protocol
header("Pragma: no-cache");
//Output MIME type
header(" Content-type: application/file");
//File length
header("Content-Length: 227685");
//Accepted range units
header("Accept-Ranges: bytes");
//Missing Time-saving file name in the file saving dialog box
header("Content-Disposition: attachment; filename=$filename");
?>

Output status value to the browser, mainly used Access control

header('HTTP/1.1 401 Unauthorized');
header('status: 401 Unauthorized');
?>

For example, to limit one If the user cannot access the page, the status can be set to 404, as shown below, so that the browser will display that the page does not exist.

header('HTTP/1.1 404 Not Found');
header("status: 404 Not Found");
?>

Note: Traditional The header must contain one of the following three headers and can only appear once. Content-Type: xxxx/yyyy Location: xxxx:yyyy/zzzz Status: nnn xxxxxx can appear more than twice in the new multipart header specification (Multipart MIME). The above is an introduction to the php header information. For more information, please refer to: php file header information detailed explanation .

Give some specific examples.

Example 1: This example redirects the browser to PHP’s official website.

Header("Location: http://www.php.net"); exit;

Example 2: You want users to get the latest information every time, not For data in Proxy or cache, you can use the following headers

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); header("Cache-Control: no-cache, must-revalidate");
header("Pragma: no-cache");

Example 3: Let the user's browser A message that the file cannot be found appears.

header("Status: 404 Not Found");

Example 4: Let users download files.

header("Content-type: application/x-gzip");
header("Content-Disposition: attachment; filename=filename");
header("Content-Description: PHP3 Generated Data" );

Instructions: No matter how many headers the page has, it will execute the last one, but it is conditional, for example:

header('Location:http://bbs.it-home.org');
header('Location:http://www.g.cn');
header('Location:http ://www.baidu.com');
//Jump to Baidu
header('Location:http://bbs.it-home.org');echo 'Programmer's Home';
header('Location :http://www.g.cn');
header('Location:http://www.baidu.com');
//Jump to google