invoice numbers

Here is a simple workaround:

1. Add 2 new fields in your database table(you can change the names as you like):
   • form_date DATE
   • form_status ENUM('1','0') DEFAULT 0
2. One time only, update your current records and set the form_status to 1 to prevent them being purged. (UPDATE table_name SET form_status = 1)
3. Insert a new empty record, get the last insert id and display it in the form. Also add that id into the from with a hidden field
4. In receiving page, if the form entries are correct, update the table with new information and set the form_status to 1.
5. Optionally in the receiving page, you can write a simple script that purges the incomplete forms older than XX days (e.g. DELETE FROM table WHERE form_date < 'YYYY-MM-DD' AND form_status = 0)

>I have a invoice form to take data and put into the database.

>I want to display the next available number from the database.

So you want to display the next available number as the invoice number on the form? That's got potentially serious problems. What if two users access the form? User A will get the same 'next available number' as user B. You're better off providing the invoice number only after the update occurs.