public function redirectUrlForUser(array $params)
    {
        if (!array_key_exists('state', $params)) {
            throw new \InvalidArgumentException('state parameter required');
        }

        if (!array_key_exists('scope', $params)) {
            throw new \InvalidArgumentException('scope parameter required');
        }

        $url = $this->getConfig('sandbox')
            ? 'https://auth.sandbox.ebay.com/oauth2/authorize?'
            : 'https://auth.ebay.com/oauth2/authorize?';

        $urlParams = [
            'client_id'     => $this->getConfig('credentials')->getAppId(),
            'redirect_uri'  => $this->getConfig('ruName'),
            'response_type' => 'code',
            'state'         => $params['state'],
            'scope'         => implode($params['scope'], ' ')

        ];

        return $url.http_build_query($urlParams, null, '&', PHP_QUERY_RFC3986);
    }
public function redirectUrlForUser(array $params)
    {
        if (!array_key_exists('state', $params)) {
            throw new \InvalidArgumentException('state parameter required');
        }

        if (!array_key_exists('scope', $params)) {
            throw new \InvalidArgumentException('scope parameter required');
        }

        $url = $this->getConfig('sandbox')
            ? 'https://auth.sandbox.ebay.com/oauth2/authorize?'
            : 'https://auth.ebay.com/oauth2/authorize?';

        $urlParams = [
            'client_id'     => $this->getConfig('credentials')->getAppId(),
            'redirect_uri'  => $this->getConfig('ruName'),
            'response_type' => 'code',
            'state'         => $params['state'],
            'scope'         => implode($params['scope'], ' ')

        ];

        return $url.http_build_query($urlParams, null, '&', PHP_QUERY_RFC3986);
    }
@param array $params An associative array with state and scope as the keys.

@return string The redirect URL.
@throws \InvalidArgumentException.