i assumed that i was working in a php application so i created a folder inside the app folder and called it solid. inside it i created a file and called it (solidresponsibility.php)
i demonstrated the format a single principle should be in a solid design pattern . Take a look at the class, you will notice that theres a class for handling the db data and a separate class was declared for handling file exportation which i created as a file in the solid folder.