How reload config file

I am a bit confused. I had the same trouble but when i came to think about it, i realized what i was doing is a mistake. Let me explain. The values in the config file are like constants relating to the settings. If my understanding is correct, these settings should be fixed and should put into our own config.php file. The file can be autoloaded each time. If changes are allowed to be made, then these should be loaded into a database table or json/ini files.