User blog comment:Kittyfire/Random Topic Blogging!/@comment-3188056-20111218024536/@comment-3394114-20111218100502

Well, I studied the reactions (not the explosion parts), but I'm not so sure on my answer. For first, both P and H2 are non-metals. And the only non-metals that react with H2 are Cl2 and N2. Therefore, a normal reaction wouldn't be possible. And that's because, as you mentioned the "valence electrons transfer", the substance wouldn't be stable. But the reaction exist, and the formula is: PH3, and it's a flammable gas.

I'd go with JS' answer xD.