Justin Bieber -- VOMITING in the Philippines

"Justin Bieber was so sick last night at his show in the Philippines, TMZ has learned, the singer repeatedly took breaks during his set to run backstage ... and barf his brains out.
Sources close to Bieber tell TMZ, JB came down with some kind of chest infection last week -- and when he hit the stage last night in Manila ... the wooziness was way too much to handle.

Gotta give the kid props -- in fact, just before his concert last night, he tweeted, "Sick as a dog ... But the show must go on." (TMZ)