How to purge bad cache from SQUID

If you’re using Squid Cache Proxy as your own proxy server, maybe you’ve experience Squid always returning the old cache even if the website itself already changed. If that’s the case then the only solution is by Purging the old cache from Squid cache. And there’s two method to do this. The first method is by deleting all of your squid cache but this would cause all of your cache lost and i don’t think you want that happen, right ? But don’t worry there’s other alternative and that’s by using PURGE command on squid.