Houston (6-5-5, 23 points) won for the second time in its past four games, while Philadelphia (3-9-2, 11 points) has lost three of the past four and six of its past eight games.
Ching knocked the penalty kick just under the crossbar inside the near post and in. Ching drew the penalty kick in the 81st minute after being taken down from behind by Philadelphia's Gabriel Farfan in the box.
Keon Daniel tied the game at 1-1 in the 46th minute, taking a pass from Brian Carroll in the center of the field, turning and shooting from 25 yards out into the left net.
Brad Davis put Houston ahead 1-0 in the 20th minute after getting a pass from Macoumba Kandji and hitting from 14 yards out on the left box just inside the far post.
Honduran national team member Oscar Boniek Garcia also got an assist on the goal, his first assist in his first game with the Dynamo since being acquired via transfer in early June.
The win extends Houston's unbeaten streak at home to 15 games, and the Dynamo haven't lost at home since a 2-0 loss to Columbus on June 18,
(Copyright 2011 Philadelphia Union. Reprinted by permission)