Come posso estrapolare il browser in uso?

[n0t]

function getBrowser($useragent)
{
    if(!empty($useragent))
    {
        $useragent = eregi_replace("^[a-z]*", " ", explode(" ", strtolower($useragent)));
        if(count($useragent) > 0)
        {
            if(in_array('windows', $useragent))
            {
                if(in_array('mozilla', $useragent))
                {
                    //hai mozilla su windows
                }
                else if(in_array('msie', $useragent))
                {
                    //hai ie su windows
                }
                //etcetc
            }
        }
    }
} 

io farei così :|