function get_os(){
$os='';
$Agent=$_SERVER['HTTP_USER_AGENT'];
if (eregi('win',$Agent)&&strpos($Agent, '95')){
$os='Windows 95';
}elseif(eregi('win 9x',$Agent)&&strpos($Agent, '4.90')){
$os='Windows ME';
}elseif(eregi('win',$Agent)&&ereg('98',$Agent)){
$os='Windows 98';
}elseif(eregi('win',$Agent)&&eregi('nt 5.0',$Agent)){
$os='Windows 2000';
}elseif(eregi('win',$Agent)&&eregi('nt 6.0',$Agent)){
$os='Windows Vista';
}elseif(eregi('win',$Agent)&&eregi('nt 6.1',$Agent)){
$os='Windows 7';
}elseif(eregi('win',$Agent)&&eregi('nt 5.1',$Agent)){
$os='Windows XP';
}elseif(eregi('win',$Agent)&&eregi('nt',$Agent)){
$os='Windows NT';
}elseif(eregi('win',$Agent)&&ereg('32',$Agent)){
$os='Windows 32';
}elseif(eregi('linux',$Agent)){
$os='Linux';
}elseif(eregi('unix',$Agent)){
$os='Unix';
}else if(eregi('sun',$Agent)&&eregi('os',$Agent)){
$os='SunOS';
}elseif(eregi('ibm',$Agent)&&eregi('os',$Agent)){
$os='IBM OS/2';
}elseif(eregi('Mac',$Agent)&&eregi('PC',$Agent)){
$os='Macintosh';
}elseif(eregi('PowerPC',$Agent)){
$os='PowerPC';
}elseif(eregi('AIX',$Agent)){
$os='AIX';
}elseif(eregi('HPUX',$Agent)){
$os='HPUX';
}elseif(eregi('NetBSD',$Agent)){
$os='NetBSD';
}elseif(eregi('BSD',$Agent)){
$os='BSD';
}elseif(ereg('OSF1',$Agent)){
$os='OSF1';
}elseif(ereg('IRIX',$Agent)){
$os='IRIX';
}elseif(eregi('FreeBSD',$Agent)){
$os='FreeBSD';
}elseif($os==''){
$os='Unknown';
}
return $os;
}
