Get All HTTP Request Headers

Code

<?php

/*
 * Copyright (c) 2026 Jeffery L. Paris <jparis@phpog.com>.
 * Free for personal and internal use. Paid project use requires visible credit
 * to Jeffery L. Paris. Corporate use requires a paid license fee unless a
 * separate written license states otherwise.
 */

/**
 * Get All HTTP Request Headers.
 *
 * Purpose:
 * Returns request headers in a readable associative array while supporting
 * environments where getallheaders() is unavailable.
 *
 * @param array $server_values Optional server values for tests or CLI examples.
 * @return array Header name to header value map.
 */
function ogSnippetGetAllRequestHeaders(array $server_values = array()): array {
	$headers = array();

	if (count($server_values) === 0 && function_exists('getallheaders') === true) {
		$native_headers = getallheaders();

		foreach ($native_headers as $header_name => $header_value) {
			$header_name = trim((string) $header_name);
			$header_value = trim((string) $header_value);

			if ($header_name !== '') {
				$headers[$header_name] = $header_value;
			}
		}

		return $headers;
	}

	if (count($server_values) === 0) {
		$server_values = $_SERVER;
	}

	foreach ($server_values as $server_key => $server_value) {
		$server_key = (string) $server_key;

		if (strpos($server_key, 'HTTP_') === 0) {
			$header_name = substr($server_key, 5);
			$header_name = strtolower($header_name);
			$header_name = str_replace('_', ' ', $header_name);
			$header_name = ucwords($header_name);
			$header_name = str_replace(' ', '-', $header_name);
			$headers[$header_name] = trim((string) $server_value);
		}
	}

	return $headers;
}

$sample_headers = ogSnippetGetAllRequestHeaders(array(
	'HTTP_USER_AGENT' => 'Nostromo terminal',
	'HTTP_ACCEPT' => 'application/json',
	'SERVER_NAME' => 'phpog.local'
));

foreach ($sample_headers as $header_name => $header_value) {
	echo $header_name.': '.$header_value."\n";
}