index.php

<?php require_once 'user_agent.php'; ?>
<!-- Now try it. -->
<?php $userAgent = new UserAgent($_SERVER['HTTP_USER_AGENT']); ?>
<?php $ua = $userAgent->getBrowser(); ?>

<p>
    <b>Your Browser:</b>
</p>
<?=$ua['name']?> <?=$ua['version']?> on <?=$ua['platform']?>

user_agent.php

<?php
class UserAgent
{
    public $bname = 'Unknown';
    public $platform = 'Unknown';
    public $version = "";
    public $browser_matches = [
        ['/MSIE/i', "MSIE", 'Internet Explorer'],
        ['/Firefox/i', "Firefox", 'Mozilla Firefox'],
        ['/Chrome/i', "Chrome", 'Google Chrome'],
        ['/Safari/i', "Safari", 'Apple Safari'],
        ['/Opera/i', 'Opera', 'Opera'],
        ['/Netscape/i', 'Netscape', 'Netscape']
    ];

    public function __construct($u_agent)
    {
        $this->u_agent = $u_agent;
    }

    public function getBrowser()
    {

        foreach ($this->browser_matches as $browser_match) {

            $regex = $browser_match[0];

            if (preg_match($regex, $this->u_agent)) {
                $this->bname = $browser_match[2];
                $this->ub = $browser_match[1];
                break;
            }

        }

        if ( preg_match('/MSIE/i', $this->u_agent) &&
            !  preg_match('/Opera/i', $this->u_agent)) {

            $this->bname = 'Internet Explorer';
            $this->ub = "MSIE";

        }

        return array(
            'userAgent' => $this->u_agent,
            'name' => $this->bname,
            'version' => $this->getVersion(),
            'platform' => $this->getPlatform(),
            'pattern' => $this->getPattern()
        );
    }

    public function getPlatform()
    {

        //First get the platform?
        if (preg_match('/linux/i', $this->u_agent)) {

            $platform = 'linux';

        } elseif (preg_match('/macintosh|mac os x/i', $this->u_agent)) {

            $platform = 'mac';

        } elseif (preg_match('/windows|win32/i', $this->u_agent)) {

            $platform = 'windows';

        }

        return $platform;
    }

    public function getPattern()
    {
        $known = array('Version', $this->ub, 'other');

        return '#(?<browser>' .
            join('|', $known) .
            ')[/ ]+(?<version>[0-9.|a-zA-Z.]*)#';
    }

    public function getVersion()
    {
        $matches = [];
        // Next get the name of the useragent yes separately and for good reason.

        // Finally get the correct version number.
        $pattern = $this->getPattern();
        if (!preg_match_all($pattern, $this->u_agent, $matches)) {
            // we have no matching number just continue
            continue;
        }

        // See how many we have.
        $i = count($matches['browser']);

        if ($i != 1) {
            //we will have two since we are not using 'other' argument yet
            //see if version is before or after the name
            if ( strripos($this->u_agent, "version")
                < strripos($this->u_agent, $this->ub)) {

                $version = $matches['version'][0];

            } else {

                $version = $matches['version'][1];

            }

        } else {

            $version = $matches['version'][0];

        }

        return ($version == null || $version == "") ? "?":$version;

    }
}
?>