function testFunction($params)
    {

        $defaults = array(
            'foo1' => $this->column,
            'bar2' => $this->columnName,
            'optionalVar' => NULL

        );

        $diff = array_diff_key($params, $defaults);
        if(!empty($diff)){
            $location = __CLASS__ . '::' . __FUNCTION__ . '()';
            $invalid = array_keys($diff);
            $valid = array_keys($defaults);
            throw new fProgrammerException("Paramaters provided for '%s' are not valid: %s. \nValid parameters: %s.", $location, implode(', ', $invalid), implode(', ', $valid));
        }
        $finalParams = array_merge($defaults, $params, $mandatory);
    // do stuff with your params
}