Know your current running operating system using php

The code below could explain in its own right, is able to show which operating system someone is using.

<?php

$user_agent = $_SERVER&#91;'HTTP_USER_AGENT'&#93;;

function getCurrentOS() { 

    global $user_agent;

    $os_platform  = "Unknown OS Platform";

    $os_array     = array(
                          '/windows nt 10/i'      =>  'Windows 10',
                          '/windows nt 6.3/i'     =>  'Windows 8.1',
                          '/windows nt 6.2/i'     =>  'Windows 8',
                          '/windows nt 6.1/i'     =>  'Windows 7',
                          '/windows nt 6.0/i'     =>  'Windows Vista',
                          '/windows nt 5.2/i'     =>  'Windows Server 2003/XP x64',
                          '/windows nt 5.1/i'     =>  'Windows XP',
                          '/windows xp/i'         =>  'Windows XP',
                          '/windows nt 5.0/i'     =>  'Windows 2000',
                          '/windows me/i'         =>  'Windows ME',
                          '/win98/i'              =>  'Windows 98',
                          '/win95/i'              =>  'Windows 95',
                          '/win16/i'              =>  'Windows 3.11',
                          '/macintosh|mac os x/i' =>  'Mac OS X',
                          '/mac_powerpc/i'        =>  'Mac OS 9',
                          '/linux/i'              =>  'Linux',
                          '/ubuntu/i'             =>  'Ubuntu',
                          '/iphone/i'             =>  'iPhone',
                          '/ipod/i'               =>  'iPod',
                          '/ipad/i'               =>  'iPad',
                          '/android/i'            =>  'Android',
                          '/blackberry/i'         =>  'BlackBerry',
                          '/webos/i'              =>  'Mobile'
                    );

    foreach ($os_array as $regex => $value)
        if (preg_match($regex, $user_agent))
            $os_platform = $value;

    return $os_platform;
}
//print the current operating system.
echo '<h2>.getCurrentOS().</h2>';

?>