PHP Warning: preg_match(): No ending delimiter '/'

Подскажите, пожалуйста, как исправить ошибку в коде:

function getOS()
{
    global $user_agent;
    $os_platform = "Unknown OS Platform";
    $os_array = array(  
    '/windows 10.0' => 'Windows 10',
        '/windows nt 10.0/i' => 'Windows 10',
        '/windows nt 6.3/i' => 'Windows 8.1',
        '/windows nt 6.2/i' => 'Windows 8',
        '/windows nt 6.1/i' => 'Windows 7',
        '/windows nt 6.0/i' => 'Windows Vista',
        '/windows nt 5.2/i' => 'Windows Server 2003/XP x64',
        '/windows nt 5.1/i' => 'Windows XP',
        '/windows xp/i' => 'Windows XP',
        '/windows nt 5.0/i' => 'Windows 2000',
        '/windows me/i' => 'Windows ME',
        '/win98/i' => 'Windows 98',
        '/win95/i' => 'Windows 95',
        '/win16/i' => 'Windows 3.11',
        '/macintosh|mac os x/i' => 'Mac OS X',
        '/mac_powerpc/i' => 'Mac OS 9',
        '/linux/i' => 'Linux',
        '/ubuntu/i' => 'Ubuntu',
        '/iphone/i' => 'iPhone',
        '/ipod/i' => 'iPod',
        '/ipad/i' => 'iPad',
        '/android/i' => 'Android',
        '/blackberry/i' => 'BlackBerry',
        '/webos/i' => 'Mobile',
    );
    foreach ($os_array as $regex => $value) {
        if (preg_match($regex, $user_agent)) {
            $os_platform = $value;
        }
    }

    return $os_platform;
}

PHP Warning: preg_match(): No ending delimiter '/'