The victory, which came after the host scored twice in the last 16 minutes to overhaul Tajikistan, also ensured group rival Yemen would qualify for Asia’s continental championship for the first time.
The pair join fellow new boys Kyrgyzstan in the draw on May 4 for next January’s tournament in the United Arab Emirates.
Younghusband, who scored a 90th minute penalty to give his side the win in Manila, said he hoped Philippine football was now on the rise.
“Hopefully this is the catalyst for more growth in Philippine football,” he said.
“In 2010, we got a lot of support from the private industry and hopefully this moment can spur a resurgence in Philippine football, get people to talk about Philippine football again.”
Football in the Philippines, and in other nations that have sat outside Asia’s established elite, is likely to receive a significant profile boost thanks to the 2015 decision to expand the quadrennial finals from 16 to 24 nations.
Throughout the last two decades, football in Asia has been dominated by the same small group of nations, who have monopolized the continent’s World Cup berths and Asian Cup success. Japan has won the title four times since 1992, Saudi Arabia, South Korea and Iran are often among the contenders, while Australia joined the confederation in 2006 and won the most recent edition on home soil three years ago.