pg_close() closes the non-persistent connection to a PostgreSQL database associated with the given connection resource.
Note: Using pg_close() is not usually necessary, as non-persistent open connections are automatically closed at the end of the script.
If there is open large object resource on the connection, do not close the connection before closing all large object resources.
PostgreSQL database connection resource. When connection is not present, the default connection is used. The default connection is the last connection made by pg_connect() or pg_pconnect().