php obtains client and server related information

$headers = array();
foreach ($_SERVER as $key => $value) {
 if ('HTTP_' == substr($key, 0, 5)) {
 $headers[str_replace('_', '-', substr($key, 5))] = $value;
 }
}
?>

Explanation: Clear in RFC Pointed out that header names are not case-sensitive.

However, not all HTTP request headers exist in $_SERVER in the form of keys starting with HTTP_. For example, Authorization, Content-Length, and Content-Type are not like this, so in order to obtain all HTTP request headers , you also need to add the following code:

if (isset($_SERVER['PHP_AUTH_DIGEST'])) {
 $header['AUTHORIZATION'] = $_SERVER['PHP_AUTH_DIGEST']);
} elseif (isset($ _SERVER['PHP_AUTH_USER']) && isset($_SERVER['PHP_AUTH_PW'])) {
 $header['AUTHORIZATION'] = base64_encode($_SERVER['PHP_AUTH_USER'] . ':' . $_SERVER['PHP_AUTH_PW'] ));
}
if (isset($_SERVER['CONTENT_LENGTH'])) {
 $header['CONTENT-LENGTH'] = $_SERVER['CONTENT_LENGTH'];
}
if (isset($_SERVER[' CONTENT_TYPE'])) {
 $header['CONTENT-TYPE'] = $_SERVER['CONTENT_TYPE'];
}
?>