How can cookies be effectively utilized to identify and track mobile devices on a website?

Cookies can be effectively utilized to identify and track mobile devices on a website by setting a unique identifier in a cookie when a mobile device visits the site. This identifier can then be used to track the device's activity and personalize the user experience accordingly.

// Set a unique identifier in a cookie for mobile devices
if( isset($_SERVER['HTTP_USER_AGENT']) && preg_match('/(android|iphone|ipad)/i', $_SERVER['HTTP_USER_AGENT']) ) {
    if( !isset($_COOKIE['mobile_device_id']) ) {
        $mobile_device_id = uniqid();
        setcookie('mobile_device_id', $mobile_device_id, time() + (86400 * 30), '/');
    }
}