How do I read any request header in PHP

Question

How should I read any header in PHP?

For example the custom header: X-Requested-With.

Answer 1

$_SERVER['HTTP_X_REQUESTED_WITH']

Answer 2

Google hit #1

http://www.php.net/apache_request_headers

<?php
$headers = apache_request_headers();

foreach ($headers as $header => $value) {
    echo "$header: $value <br />\n";
}
?>

See Also

apache_response_headers() - Fetch all HTTP response headers