public function getGrade()
{
//Get the hidden value.
$response = $this->buildGetRequest(self::ZF_GRADE_URI, [], $this->headers);
$viewstate = $this->parserOthersHiddenValue($response->getBody());
$post['__EVENTTARGET'] = '';
$post['__EVENTARGUMENT'] = '';
$post['__VIEWSTATE'] = $viewstate;
$post['hidLanguage'] = '';
$post['ddlXN'] = '';
$post['ddlXQ'] = '';
$post['ddl_kcxz'] = '';
$post['btn_zcj'] = iconv('utf-8', 'gb2312', '历年成绩');
$response = $this->buildPostRequest(self::ZF_GRADE_URI, [], $post, $this->headers);
return $this->parserCommonTable($response->getBody(), '#Datagrid1');
}