It doesn't exist anymore.
What replaced it is the 2 day/2 park and 3 day/3 park tickets. These tickets allow entry to only one park per day. You cannot park hop with these tickets but you can leave and return to the same park the same day.
You can upgrade a single day ticket to a 2 day or 3 day. Second and third days must be bought at the time of original purchase on the first day OR before the end of the business day of the date of the first day's purchase. There is a $5 savings over the price of two one day tickets when you get the 2 day/2 park and a $10 savings over the price of three one day tickets when you get the 3 day/3 park.
The second day ticket will expire 4 days after purchase and the third day will expire 6 days after purchse. These tickets can only be purchased at a WDW major park ticket booth, Guest Relations, resort front desk, or Guest Services.