What does the PHP header function do? Introduction to PHP header function (with code)

What does the php header function do? In php, the header function can be used as two special headers to send status codes. It can replace the previous header of the same type, or it can force the value of the HTTP response to be specified; then, let's take a look at the specific content.

Let’s take a look at the definition in the official document first

(PHP 4, PHP 5, PHP 7)

header —Send native HTTP header

1 void header ( string $string [, bool $replace = true [, int $http_response_code ]] )

Parameters:

string

There are two special head of. The first one starting with "HTTP/" (case is not significant) will be used to calculate the HTTP status code to be sent. For example, if you use a PHP script on the Apache server to handle requests for files that do not exist (using theErrorDocumentdirective), you will hope that the script responds with the correct status code.

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The second special case is the "Location:" header information. It not only sends the message to the browser, but also returns aREDIRECT(302) status code to the browser, unless the status code has been set to201or ## in advance. #3xx.

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replace

• Optional parameterreplaceIndicates whether to use the following The header replaces the previous header of the same type. Replaced by default. If you passFALSE, you can force the same header information to coexist. For example:

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Copy after login

http_response_code

Forces the value of the HTTP response. Note that this parameter is only valid when the message string (string) is not empty.

The common uses of the header function are as follows:

　1. Redirection

header('Location: http://www.example.com/');

2. Specified content:

header ('Content-type: application/pdf'); : application/pdf');

　　　 //Specify the content as an attachment and specify the name for download display

　　header('Content -Disposition: attachment; filename="downloaded.pdf"');##　　　 //Open the file and output

　　readfile('original .pdf');

The above code can produce the effect of a file dialog box in the browser

4. Allow users to obtain the latest information and Data instead of caching

Header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1

Detailed example:

Detailed explanation of php header function

Usage of PHP header() function

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