Simple PHP website that checks if username and password exist in mysql database

I wont make this too complicated but I need help creating a website that checks to see if a username and password exists in a mysl database that is created. This website should be made in php. This website should contain 3 parts: Frontend Middle-end Backend. It also needs to follow a specific format. Please see the Screenshot i uploaded. The frontend : -displays the login check page -Be able to curl to the middle -also sending data via POST and receiving via JSON The middle end -should contain code that is responsible for curling to the backend , also sending data via POST and receiving via JSON The back end -Contains both MSQL server and php file(s) that deals with connecting the SQL server and passing the username and password info to the middle Please refer to picture i uploaded which shows the exact format to follow. I can upload a sample example if needed