The Phillies and Astros have met in the postseason before, back when Houston was a National League team.
That was the 1980 NLCS, won by the Phillies three games to two — of course, at the time the LCS were best-of-five. Four of those five games went into extra innings, including the decisive Game 5. In that game, Houston had a 5-2 lead heading into the eighth. The Phillies took a 7-5 lead with a five-run eighth, but a pair of run-scoring singles made it 7-7 going to the ninth. The Phillies eventually took an 8-7 lead on a Garry Maddox RBI double in the top of the 10th, and Houston went down 1-2-3, sending the Phillies to their first World Series in 30 years.