[IntoRain]

I believe Infernette has a system like that on her website (two separate inventories). It's doable.

The inventory is just a group of tables in phpMyAdmin (the one with all the items and the one that associates an item and its owner). So, if you create a table for collectables (instead of a table with all the items and their functions) plus another table to associate an item, a quantity and an owner, it should work. You could copy the code from the inventory (and I guess some from the item class) and try to repeat what's done there and instead of getting the items from that table, you could go get them from the new table (the one that associates collectables and people). But it depends also on how you would obtain them, since that's important to fill the tables.

And I'm also thinking about this without actually looking at the code, but it's something along those lines, I will have to make one for a feature I'm implementing on my test site so I don't mind sharing the code when it's done