Season 3

It was stated by Swampy Marsh and Dan Povenmire that Phineas and Ferb there would be at least enough days of summer left for a third season.

News began appearing on June 7, 2009 that this was the case, and Disney XD MediaNet issued a press release two days later confirming it.

Known episode plots for Season 3 include Candace and Jeremy finally becoming boyfriend and girlfriend, and Phineas & Ferb building another rollercoaster as a full-on musical. 

The exact number of episodes ordered was not included in the press release, nor was the premiere date. Nor did I mention songs.