I was searching for a solution to my problem and didn't find one. Basically the user can add/delete information which will delete the row. The user can also arrange this information up/down which would also switch the primary keys (called placeholder). The problems are is that if the user deletes a row it won't move the placeholder int up one. I was wondering If there's any way to move the rows up and arrange them starting from 1.
You shouldn't amend auto increment. It's part of the database design. You should use another column name as the identifier, ID perhaps?