src/Zend/Http/UserAgent.php
public function getUserAgent()
    {
        if (null === ($ua = $this->getServerValue('http_user_agent'))) {
            $ua = self::DEFAULT_HTTP_USER_AGENT;
            $this->setUserAgent($ua);
        }

        return $ua;
    }
public function getUserAgent()
    {
        if (null === ($ua = $this->getServerValue('http_user_agent'))) {
            $ua = self::DEFAULT_HTTP_USER_AGENT;
            $this->setUserAgent($ua);
        }

        return $ua;
    }
public function getUserAgent ( ) { if ( null === ( $ ua = $ this -> getServerValue ( 'http_user_agent' ) ) ) { $ ua = self :: DEFAULT_HTTP_USER_AGENT ; $ this -> setUserAgent ( $ ua ) ; } return $ ua ; }
Returns the User Agent value

If $userAgent param is null, the value of $_server['HTTP_USER_AGENT'] is
returned.

@return string
Returns the User Agent value