1)UI is using adobe flex; PHP is the scripting page; mySQL the database
2)UI includes a canvas to draw; you can draw using the mouse pointer inside the canvas
3)A save button below the canvas, by clicking this whatever is drawn on the canvas will be saved as a jpeg/gif image in the database. (or whatever format is suitable)
4)The drawing on the canvas should be converted to jpeg/gif (or whatever is suitable), pass it to the php page, the page will save it to a BLOB column in the database
5)Another canvas which is blank, a load button will retrieve the saved image and show it in the new canvas. User can draw again on top of this loaded drawing and the final drawing can be saved again as mentioned above.