Q: What database hostname should I use in Google Cloud Platform (PHP) 
First of all, I'd like to say that I am relatively new to GCP.

Currently hosting a codeigniter app with Google Cloud Platform. I already imported my database successfully to Google Cloud SQL. However, when I try to connect, I get the following error: mysqli::real_connect(): php_network_getaddresses: getaddrinfo failed: No such host is known.
Basically, doing the equivalent of PHP's mysqli::real_connect($hostname, $username, $password, $database, $port, $socket, $client_flags))
So my question is, what is the correct hostname/how do you get the hostname for your database on Google Cloud Platform?
The host name I'm currently using
your_project_name:your_region:your_instance where each of those corresponds to my project. I got this information from the docs. Specifically used the configuration settings listed there and assumed cloudsql_connection_name: your_project_name:your_region:your_instancecould be used as host name.
Is there something I'm missing?
Also, any tips for hosting codeigniter apps with GCP?

A: Use the output of the this command if need FQDN:
kubectl exec "your_db_pod_name"  -- hostname --fqdn

