php csv生成器不输出文件，多个选择不传递值

I am building a CSV generator that takes a selection of areas from a multiple select box and loops through the selected to pop out a separate CSV for each item based on database info, or at least it is supposed to, it keeps popping out a PHP file with my header include and then an error about an undefined $filename variable once for each item I have selected, it does not pass the Area_ID at all from the multiple select. Another oddity (at least as far as I can see, probably normal but seems odd to me) is that the CSVGen function if included from a separate file requires my database connect string inside the function where the page that calls it has my DB connect include present, seems impractical to open up to 2 dozen new sessions instead of using the one I've already opened.I am building a CSV generator that takes a sele