/**
* 获取令牌
*/
function getAccessToken()
{

	$wxapp = WxappModel::detail();//获取小程序配置信息
    //判断现有的access_token是否过期，过期重新获取
	if($wxapp['expires_in'] >= time()){
    	//不过期直接返回
		$access_token=$wxapp['access_token'];
	}else{
		//重新获取
		$config = ConfigModel::detail();	//获取第三方配置
        //请求URL
		$url = 'https://api.weixin.qq.com/cgi-bin/component/api_authorizer_token?component_access_token='.$config['component_access_token'];
        //请求参数
		$data ='{"component_appid": "'.$config['app_id'].'","authorizer_appid": "'.$wxapp['app_id'].'","authorizer_refresh_token": "'.$wxapp['authorizer_refresh_token'].'"}';
		$result = http_request($url,$data);
		$token = json_decode($result,true);
		$wxapp['access_token'] = $token['authorizer_access_token'];
		$wxapp['expires_in'] = time()+7000; //2个小时候过期，少加200秒
		//$wxapp['authorizer_refresh_token'] = $token['authorizer_refresh_token'];
		$access_token = $token['authorizer_access_token'];
		$wxapp->save();//保存最新的令牌access_token和过期时间
	}
	return $access_token;		
}