core/Form.php
public function getError(string $name)
    {
        return isset($this->fields[$name]) ? $this->fields[$name]->error : '';
    }
public function getError(string $name)
    {
        return isset($this->fields[$name]) ? $this->fields[$name]->error : '';
    }
获取错误
@param string $name
@return null|string