Master PHP’s header() Function: Redirects, Headers, and Advanced Uses

In PHP, the header() function is essential for page redirects and setting HTTP response headers. This article explains its usage and provides code examples.

Basic syntax of header()

header(string $header, bool $replace = true, int $http_response_code = 0): bool

$header

(required): the HTTP header string to send, e.g., "Content-Type: text/html;charset=utf-8". $replace (optional): whether to replace a previous header of the same name; true by default. $http_response_code (optional): the HTTP status code to set.

Common scenarios and code examples

Page redirection

The header() function can redirect users to a specified URL.

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

Setting HTTP response headers

Use header() to set headers such as Content-Type or Content-Disposition.

header("Content-Type: application/json");

Setting HTTP status codes

Set status codes like 200 for success or 404 for not found.

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

Preventing page caching

Send Cache-Control, Pragma, and Expires headers to disable caching.

header("Cache-Control: no-cache, no-store, must-revalidate");
header("Pragma: no-cache");
header("Expires: 0");

File download

Set Content-Disposition to attachment and appropriate Content-Type and Content-Length to trigger a file download.

header("Content-Disposition: attachment; filename=example.pdf");
header("Content-Type: application/pdf");
header("Content-Length: " . filesize("example.pdf"));
readfile("example.pdf");

The header() function is versatile for redirects, header manipulation, status codes, cache control, and file downloads, and developers should understand its parameters to use it effectively.