src/Common/Helper.php
public static function getGatewayClassName($shortName)
    {
        if (0 === strpos($shortName, '\\')) {
            return $shortName;
        }

        // replace underscores with namespace marker, PSR-0 style
        $shortName = str_replace('_', '\\', $shortName);
        if (false === strpos($shortName, '\\')) {
            $shortName .= '\\';
        }

        return '\\Omnipay\\'.$shortName.'Gateway';
    }
public static function getGatewayClassName($shortName)
    {
        if (0 === strpos($shortName, '\\')) {
            return $shortName;
        }

        // replace underscores with namespace marker, PSR-0 style
        $shortName = str_replace('_', '\\', $shortName);
        if (false === strpos($shortName, '\\')) {
            $shortName .= '\\';
        }

        return '\\Omnipay\\'.$shortName.'Gateway';
    }
Resolve a short gateway name to a full namespaced gateway class.

Class names beginning with a namespace marker (\) are left intact.
Non-namespaced classes are expected to be in the \Omnipay namespace, e.g.:

\Custom\Gateway     => \Custom\Gateway
\Custom_Gateway     => \Custom_Gateway
Stripe              => \Omnipay\Stripe\Gateway
PayPal\Express      => \Omnipay\PayPal\ExpressGateway
PayPal_Express      => \Omnipay\PayPal\ExpressGateway

@param  string  $shortName The short gateway name
@return string  The fully namespaced gateway class name