Buenas, soy medio nuevo en programación php, andaba buscando un codigo que me diera el modelo del navegador y el SO de mis visitantes en mi web hasta que lo encontré, pero no lo puedo hacer funcionar cuando lo subo me salta el siguiente error:

Warning: preg_match_all() [function.preg-match-all]: Compilation failed: unrecognized character after (?< at offset 3 in /home/.../public_html/prueba/prueba3.php on line 46

el codigo es el siguiente:
<?php
function getBrowser()
{
$u_agent = $_SERVER['HTTP_USER_AGENT'];
$bname = 'Unknown';
$platform = 'Unknown';
$version= "";


// Next get the name of the useragent yes seperately and for good reason
if(preg_match('/MSIE/i',$u_agent) && !preg_match('/Opera/i',$u_agent))
{
$bname = 'Internet Explorer';
$ub = "MSIE";
}
elseif(preg_match('/Firefox/i',$u_agent))
{
$bname = 'Mozilla Firefox';
$ub = "Firefox";
}
elseif(preg_match('/Chrome/i',$u_agent))
{
$bname = 'Google Chrome';
$ub = "Chrome";
}
elseif(preg_match('/Safari/i',$u_agent))
{
$bname = 'Apple Safari';
$ub = "Safari";
}
elseif(preg_match('/Opera/i',$u_agent))
{
$bname = 'Opera';
$ub = "Opera";
}
elseif(preg_match('/Netscape/i',$u_agent))
{
$bname = 'Netscape';
$ub = "Netscape";
}

// finally get the correct version number
$known = array('Version', $ub, 'other');
$pattern = '#(?<browser>' . join('|', $known) .
')[/ ]+(?<version>[0-9.|a-zA-Z.]*)#';
if (!preg_match_all($pattern, $u_agent, $matches)) {
// we have no matching number just continue
}

// see how many we have
$i = count($matches['browser']);
if ($i != 1) {
//we will have two since we are not using 'other' argument yet
//see if version is before or after the name
if (strripos($u_agent,"Version") < strripos($u_agent,$ub)){
$version= $matches['version'][0];
}
else {
$version= $matches['version'][1];
}
}
else {
$version= $matches['version'][0];
}

// check if we have a number
if ($version==null || $version=="") {$version="?";}

return array(
'userAgent' => $u_agent,
'name' => $bname,
'version' => $version,
'pattern' => $pattern
);
}



function getOs()
{
$useragent= strtolower($_SERVER['HTTP_USER_AGENT']);

//winxp
if (strpos($useragent, 'windows nt 5.1') !== FALSE) {
return 'Windows XP';
}
elseif (strpos($useragent, 'windows nt 6.1') !== FALSE) {
return 'Windows 7';
}
elseif (strpos($useragent, 'windows nt 6.0') !== FALSE) {
return 'Windows Vista';
}
elseif (strpos($useragent, 'windows 98') !== FALSE) {
return 'Windows 98';
}
elseif (strpos($useragent, 'windows nt 5.0') !== FALSE) {
return 'Windows 2000';
}
elseif (strpos($useragent, 'windows nt 5.2') !== FALSE) {
return 'Windows 2003 Server';
}
elseif (strpos($useragent, 'windows nt') !== FALSE) {
return 'Windows NT';
}
elseif (strpos($useragent, 'win 9x 4.90') !== FALSE && strpos($useragent, 'win me')) {
return 'Windows ME';
}
elseif (strpos($useragent, 'win ce') !== FALSE) {
return 'Windows CE';
}
elseif (strpos($useragent, 'win 9x 4.90') !== FALSE) {
return 'Windows ME';
}
elseif (strpos($useragent, 'windows phone') !== FALSE) {
return 'Windows Phone';
}
elseif (strpos($useragent, 'iphone') !== FALSE) {
return 'iPhone';
}
// experimental
elseif (strpos($useragent, 'ipad') !== FALSE) {
return 'iPad';
}
elseif (strpos($useragent, 'webos') !== FALSE) {
return 'webOS';
}
elseif (strpos($useragent, 'symbian') !== FALSE) {
return 'Symbian';
}
elseif (strpos($useragent, 'android') !== FALSE) {
return 'Android';
}
elseif (strpos($useragent, 'blackberry') !== FALSE) {
return 'Blackberry';
}
elseif (strpos($useragent, 'mac os x') !== FALSE) {
return 'Mac OS X';
}
elseif (strpos($useragent, 'macintosh') !== FALSE) {
return 'Macintosh';
}
elseif (strpos($useragent, 'linux') !== FALSE) {
return 'Linux';
}
elseif (strpos($useragent, 'freebsd') !== FALSE) {
return 'Free BSD';
}
elseif (strpos($useragent, 'symbian') !== FALSE) {
return 'Symbian';
}
else
{
return 'Desconocido';
}
}

$sistema.="Sistema Operativo: ".getOs();
$ua=getBrowser();
$sistema.="<br> Navegador: ".$ua['name'] . " " . $ua['version'];
$sistema.="<br > Agente Completo: " .$_SERVER['HTTP_USER_AGENT'];
echo $sistema;

?>

lo mas raro es que lo probé en localhost y funciono bien...
agradezco su ayuda...