public static function getAreaInfoByCityId($city_id){
$REDIS_KEY = "getAreaInfoByCityId:$city_id";
//读缓存
$area_info = S($REDIS_KEY);
if( ! $area_info )
{
//读数据库
$area_info = M('area_city')->where(['area_id' => $city_id])->find();
//存入缓存
S($REDIS_KEY , $area_info , 60);
}
return $area_info;
}