This page is to add a book to the stock... With the way foreign keys are set up, the books have to exist!
Warning: Undefined array key "ISBN" in /System/Volumes/Data/Web/12DGT/ws20181/books/add_book.php on line 21

Warning: Undefined array key "stock" in /System/Volumes/Data/Web/12DGT/ws20181/books/add_book.php on line 21
Adding to store... Stock