You can always have your script create and modify files (assuming your script can get write permissions on the host server). However, this means managing everything yourself including all of the functionality provided by SELECT, UPDATE, INSERT, and DELETE. This is a major pain. I would only attempt this for very small datasets.
PHP does, however, make this easier with the functions 'file', 'explode', and 'implode'. A small data file can be read directly into an array and manipulated quite easily with these functions.