$useragent = $_SERVER['HTTP_USER_AGENT'] . "<br/>";
function get_os_name($useragent){

	global $useragent;
	$ostypes = array(
		'Win311' => 'Win16',
		'Win95' => '(Windows 95)|(Win95)|(Windows_95)',
		'WinME' => '(Windows 98)|(Win 9x 4.90)|(Windows ME)',
		'Windows 98' => '(Windows 98)|(Win98)',
		'Windows 2000' => '(Windows NT 5.0)|(Windows 2000)',
		'Windows XP' => '(Windows NT 5.1)|(Windows XP)',
		'WinServer2003' => '(Windows NT 5.2)',
		'WinVista' => '(Windows NT 6.0)',
		'Windows 7' => '(Windows NT 6.1)',
		'Windows 8' => '(Windows NT 6.2)',
		'WinNT' => '(Windows NT 4.0)|(WinNT4.0)|(WinNT)|(Windows NT)',
		'OpenBSD' => 'OpenBSD',
		'SunOS' => 'SunOS',
		'Ubuntu' => 'Ubuntu',
		'Android' => 'Android',
		'Linux' => '(Linux)|(X11)',
		'iPhone' => 'iPhone',
		'iPad' => 'iPad',
		'MacOS' => '(Mac_PowerPC)|(Macintosh)',
		'QNX' => 'QNX',
		'BeOS' => 'BeOS',
		'OS2' => 'OS/2',
		'SearchBot' => '(nuhk)|(Googlebot)|(Yammybot)|(Openbot)|(Slurp)|(MSNBot)|(Ask Jeeves/Teoma)|(ia_archiver)'
	);

	$useragent = strtolower($useragent ? $useragent : $_SERVER['HTTP_USER_AGENT']);
	foreach ($ostypes as $os => $pattern){
		if (preg_match('/' . $pattern . '/i', $useragent))
			return $os;
		
	}
	return 'Unknown';
}

$your_os = get_os_name($useragent);
echo "<p align='center'><font style='color:green;'><b>Senin Kullandığın İşletim Sistemi :  <font style='color:red;'>".strtoupper($your_os)."</font></b></font></p>";