PHP header function tutorial_PHP tutorial

The header() function sends a raw HTTP header to the client. header(string,replace,http_response_code) It is important to see that header() must be sent before any actual output is called ​

PHP header function tutorial

Definition and usage
The header() function sends a raw HTTP header to the client.

It's important to see that headers ( ) must be sent before any actual output is called (in PHP 4 and later, you can use output buffering to solve this problem):

// This results in an error.
// The output above is before the header() call
header('Location: http://www.example.com/');
?>

Syntax:

header(string,replace,http_response_code)

Parameter	Description
string	必需的。指定的标题字符串发送
replace	任择。指示是否标题应取代以前或添加第二个标题。预设值是true （将取代） 。假（允许多个标题同一类型）
http_response_code	任择。部队的HTTP响应代码到指定的值（可在PHP 4.3和更高）

Description

string

Required. The specified header string is sent

replace

Optional. Indicates whether the title should replace the previous one or add a second title. The default value is true (will be replaced). false (allows multiple titles of the same type)

http_response_code

Optional. Forces the HTTP response code to a specified value (available in PHP 4.3 and higher)

Tips and Instructions NOTE: As of PHP 4.4 this feature prevents more than one header from being sent at once. This is a protection against header injection attacks. Example 1 Prevent page caching:

// Date in the pastheader("Expires: Mon, 26 Jul 1997 05:00:00 GMT");header("Cache-Control: no-cache");header("Pragma: no-cache") ;

Example 2 Let the user be prompted to save the generated PDF file (the content-disposition header is used to provide suggested filenames and force the browser to show the save dialog):

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

// It will be called downloaded.pdfheader("Content-Disposition:attachment;filename='downloaded.pdf'");

// The PDF source is in original.pdfreadfile("original.pdf");

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