PHP DNS Resolver Issue

I ran into a very nasty issue with 3rd-party services in client projects the past two days. Suddenly all connections to external APIs (Campaign Monitor, Google Maps Geo Locator, Algolia, etc.) got denied because of unresolved hosts. It took me forever to figure out, that it’s not a Kirby issue or any other issue in my code, but in fact a problem on Ubuntu servers. The solution is really simple. You just have to restart the PHP service or ask your hosting company to do so. But since it took me a couple hours I though it might be helpful for you in case you are fighting with the same issues: