Hello Reader! If you want to detect the OS version of user though the web browser. Then you can use the library code below:-

<?php 
$OSList = array
(
// Match user agent string with operating systems
'Windows 3.11' => 'Win16',
'Windows 95' => '(Windows 95)|(Win95)|(Windows_95)',
'Windows 98' => '(Windows 98)|(Win98)',
'Windows 2000' => '(Windows NT 5.0)|(Windows 2000)',
'Windows XP' => '(Windows NT 5.1)|(Windows XP)',
'Windows Server 2003' => '(Windows NT 5.2)',
'Windows Vista' => '(Windows NT 6.0)',
'Windows 7' => '(Windows NT 7.0)',
'Windows NT 4.0' => '(Windows NT 4.0)|(WinNT4.0)|(WinNT)|(Windows NT)',
'Windows ME' => 'Windows ME',
'Open BSD' => 'OpenBSD',
'Sun OS' => 'SunOS',
'Linux' => '(Linux)|(X11)',
'Mac OS' => '(Mac_PowerPC)|(Macintosh)',
'QNX' => 'QNX',
'BeOS' => 'BeOS',
'OS/2' => 'OS/2',
'Search Bot'=>'(nuhk)|(Googlebot)|(Yammybot)|(Openbot)|(Slurp)|(MSNBot)|(Ask Jeeves/Teoma)|(ia_archiver)'
);
// Loop through the array of user agents and matching operating systems
foreach($OSList as $CurrOS=>$Match)
{
// Find a match
if (eregi($Match, $_SERVER['HTTP_USER_AGENT']))
{
// We found the correct match
break;
}
}
// You are using ...
echo "You are using ".$CurrOS;
?>