public static function generateInputField($name, 
                                              $type, 
                                              $currentValue="", 
                                              $placeholder="")
    {
        $type = strtolower($type);
        
        if ($type === 'button')
        {
            $msg = 'Developer error: please use the generateButton function ' . 
                   'instead to create buttons.';
            throw new \Exception($msg);
        }
        
        if ($type == 'submit')
        {
            $msg = 'Developer error: please use the generateSubmitButton ' . 
                   'function instead to create submit buttons.';
            throw new \Exception($msg);
        }
                
        $html = '<input ' .
                    'type="' . $type . '" ' .
                    'name="' . $name .'" ' . 
                    'placeholder="' . $placeholder . '" ' . 
                    'value="' . $currentValue . '" >';

        return $html;
    }