PHP header () function
Complete PHP HTTP Reference Manual Definition and Usage
header () function to the client to send raw HTTP headers.
It is important to recognize that you must call the header () function before any actual output is sent (in PHP 4 and later versions, you can use output buffering to solve this problem):
<?php
// This results in an error.
// The output above is before the header() call
header('Location: http://www.example.com/');
?>
grammar
| 参数 | 描述 |
|---|---|
| string | 必需。规定要发送的报头字符串。 |
| replace | 可选。指示该报头是否替换之前的报头，或添加第二个报头。默认是 TRUE（替换）。FALSE（允许相同类型的多个报头）。 |
| http_response_code | 可选。把 HTTP 响应代码强制为指定的值。（PHP 4.3 以及更高版本可用） |
Tips and Notes
NOTE: Starting after PHP 4.4, the function to prevent send multiple headers.This is a protection against head injection attacks.
Example 1
Disable page caching:
// Date in the past
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Cache-Control: no-cache");
header("Pragma: no-cache");
?>
<html>
<body>
...
...
Note: Users may set some options to change the default browser cache settings.By sending the headers above, you can override any of these settings, do not force the browser cache!
Example 2
Prompt the user to save a generated PDF file (Content-Disposition header is used to provide a recommended filename and force the browser to display the save dialog):
header("Content-type:application/pdf");
// It will be called downloaded.pdf
header("Content-Disposition:attachment;filename='downloaded.pdf'");
// The PDF source is in original.pdf
readfile("original.pdf");
?>
<html>
<body>
...
...
NOTE: Microsoft IE 5.5 more than the existence of a mechanism to prevent the bug.By upgrading to Service Pack 2 or later versions, you can fix the bug.
Complete PHP HTTP Reference Manual