Okay, so there's some definition of operations you need to be concerned with:
1: Add part number (up to 20)
2: Delete single part number
3: Delete all part numbers
4: Uh... what? Once the list is cleared it would be gone, no?
This would get me out of using arrays.
It would get you out of using -persistant- arrays. You'll still be using temporary arrays during the page loads.
Just had a thought - I then need to restrict the 'remembered' table to the last 20 part numbers - somehow...
I'm moderately sure you can do this through a semi-complex conditional query, but i'd have to defer to the gurus of SQL on that one. You could do it with a select-then-insert query pair, also.
May be using cookies is the way to go - may be less complicated.
In the meantime, I have tried a foreach loop and a for loop to try changing the index on each post and build the array that way but as you probably know this just populates the whole array index 0 through 20 with the same number each time I post. So I really need direction on building the array and displaying the past entries.
So use the part number as the key of the array, not the value. You can check size with count().