Server-side detection of CSS3 Gradients

/**
 * Attempts to ascertain user agent support for CSS-based gradients.
 *
 * @version 1.1
 * @param string $ua UA string to analyse. Defaults to the current User-Agent.
 * @return bool True if browser appears capable of supporting CSS gradients.
 */
function gradient_support($ua = ''){
    $agent      =   empty($ua) ? $_SERVER['HTTP_USER_AGENT'] : (string) $ua;

    //  Gecko 1.9.2
    if(preg_match("#(Firefox|Thunderbird|Fennec)\/([\w\.]+)#", $agent, $match)){
        switch($match[1]){
            case 'Firefox' : return(version_compare('3.6', $match[2]) < 1);     break;
            case 'Thunderbird' : return(version_compare('3.1', $match[2]) < 1); break;
            case 'Fennec' : return(version_compare('1.0a1', $match[1]) < 1);    break;
        }
    }

    //  Chrome (Apparently supported in all builds)
    else if(preg_match("#Chrome\/#", $agent, $match))
        return true;


    //  Safari 4.0
    else if(preg_match("#Safari\/#", $agent, $match) && preg_match("#Version\/([\w\.]+)#", $agent, $match))
        return(version_compare('4.0', $match[1]) < 1);


    //  Internet Explorer 10.0
    else if(preg_match("#MSIE ([\w\.]+)#", $agent, $match))
        return(version_compare('10.0', $match[1]) < 1);


    //  Presto 2.8+ (Opera 11.10)
    else if(preg_match("#Presto\/([\w\.]+)#", $agent, $match))
        return(version_compare('2.8', $match[1]) < 1);

    return false;
}