PHPDaemon\Clients\Mongo\Pool::_paramFields PHP Method

    protected function _paramFields($f)
    {
        if (is_string($f)) {
            $f = array_map('trim', explode(',', $f));
        }
        if (!is_array($f) || sizeof($f) === 0) {
            return null;
        }
        if (!isset($f[0])) {
            return $f;
        }
        $p = [];
        foreach ($f as $k) {
            $p[$k] = 1;
        }
        return $p;
    }