ImportExportPlugin::isAllowedMethod PHP Method

    function isAllowedMethod($url)
    {
        $allowedPrefixes = array('http://', 'ftp://', 'https://', 'ftps://');
        foreach ($allowedPrefixes as $prefix) {
            if (substr($url, 0, strlen($prefix)) === $prefix) {
                return true;
            }
        }
        return false;
    }