HTTP Request Headers

HTTP request headers are sent by the client to the server at the start of an HTTP request. They carry metadata about the client, the requested resource, and the desired response format.

Request headers are available in the $_SERVER superglobal with the HTTP_ prefix, e.g., $_SERVER['HTTP_ACCEPT'], or through getallheaders() for the full list.

Common request headers include Accept, Authorization, Content-Type, User-Agent, and Cookie.

<?php

// Read a specific request header
$userAgent = $_SERVER['HTTP_USER_AGENT'] ?? 'unknown';

// Read all request headers
$requestHeaders = getallheaders();

foreach ($requestHeaders as $name => $value) {
    echo "$name: $value", PHP_EOL;
}

?>

Documentation

Related : HTTP Headers, Hyper Text Transfer Protocol (HTTP), Headers, $_SERVER, HTTP Code, Redirect, Search Engine Optimization (SEO)