PHP 5.2 function analysis: How to use the header function to set HTTP response headers

PHP 5.2 Function Analysis: How to use the header function to set the HTTP response header

Introduction:
In Web development, setting the HTTP response header is very important, it can affect the browser's return to the server Analysis and display of content. The header function provided by PHP can help us set these HTTP response headers. This article will introduce in detail how to use the header function in PHP 5.2 version.

1. Syntax and description of header function
The general syntax of header function is:
header(string $header_string, bool $replace = true, int $http_response_code)

where , the $header_string parameter is the HTTP header information to be set, the $replace parameter indicates whether to replace the existing header information of the same type, the default is true replacement, the $http_response_code parameter indicates the returned HTTP response status code, the default value is 200.

Note: The header function must be called before any actual output.

2. Set common HTTP response headers

1. Set Content-Type
   The Content-Type header is used to specify the type of content returned by the server. The most common It is set to "text/html" to represent an HTML document. The code example is as follows:

   header("Content-Type: text/html;charset=utf-8");

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2. Set the Location
   Location header to specify the redirection path. The code example is as follows:

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

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3. Set Cache-Control
   The Cache-Control header is used to control the browser cache strategy. The code example is as follows:

   header("Cache-Control: no-cache, must-revalidate");

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4. Set Expires
   The Expires header is used to specify the time when the content expires. The code example is as follows:

   header("Expires: Thu, 19 Nov 1981 08:52:00 GMT");

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5. Set Content-Disposition
   The Content-Disposition header is used to specify the behavior of the browser when downloading data. Code examples are as follows:

   header("Content-Disposition: attachment; filename="example.pdf"");

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3. Other common usages

1. Set the HTTP response status code and text description
   You can pass the third Parameter $http_response_code to set the HTTP response status code, for example, set to 404 Not Found:

   header("HTTP/1.1 404 Not Found");

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2. Sending of original HTTP header information
   In addition to common HTTP header information, the header function can also Used to send arbitrary raw HTTP headers. For example, send a custom header:

   header("X-Custom-Header: Custom Value");

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3. Clear the previously set HTTP response header
   If you want to clear the previously set HTTP response header, you can set the $replace parameter Implemented as false. The code example is as follows:

   header("Content-Type: text/html;charset=utf-8", false);
   header("X-Custom-Header: Custom Value");

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End:
Through the introduction of this article, we understand the usage of the header function in PHP 5.2 version. In web development, we can flexibly set various functions as needed. HTTP response header to better control the browser's parsing and display of the content returned by the server. I hope this article can be helpful to everyone.

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