When we are finished querying the database, it is recommended to close the connection to free up resources.
Object oriented style
Note: The connection to the server will be closed as soon as the execution of the script ends, unless it's closed earlier by explicitly calling the close connection function.
Use Case: If our script has a fair amount of processing to perform after fetching the result and has retrieved the full result set, we definitely should close the connection. If we were not to, there's a chance the MySQL server will reach its connection limit when the web server is under heavy use.