$_SERVER['HTTP_USER_AGENT']
CCBot/2.0 (https://commoncrawl.org/faq/)
Simple mobile/desktop detection example:
<?php
$get_user_agent = $_SERVER['HTTP_USER_AGENT'];
if (preg_match('/android|mobile|tablet|ip(od|hone)/i', $get_user_agent)) { echo 'Mobile'; } else { echo 'Desktop'; }
?>
Result: Desktop