You might have wrong db structure.
Separate the user table and order table. User table should has ID numbers, names and ordered. Also, order table should has ID numbers, names and quantities.
For example, if one user click cheese to order, then update the ordered field (insert the ID number of the ordered item) from user table where username/id is the user/user's id who made the order. If the user made more than one orders, you can store the id numbers of the ordered item together with comma (1,2,3 etc).
And then, you might update quantities field from order table where the field 'quantities' is Cheese. So, you can analyze how many orders exist for each item. Once, the user has finished the ordered process or logged out without finishing the order process, you must remove the order from that user.
Hope this help.
Zero13
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