If you want code is running on multiple servers with different environments,then we have need to use dirname(FILE) in an include or include_once statement. reason is follows. 1. Do not give absolute path to include files on your server. 2. Dynamically calculate the full path like absolute path.
Use a combination of dirname(FILE) and subsequent calls to itself until you reach to the home of your '/myfile.php'. Then attach this variable that contains the path to your included files.