LAS VEGAS - Todd Phillips is smiling. He has good reason for cheer. As director of one of the hottest comedies of the year, "The Hangover," the 39-year-old has already established himself among Hollywood's firmament.

And the release of the DVD and Blu-ray versions of the film just before the holidays has made Phillips even merrier.

Humor is nothing new to the producer-director who helmed "Old School," "School for Scoundrels," "Road Trip" and "Starsky and Hutch."

"I had a sense of humor when I was a kid," he said, seated at a linen-covered table in a vacant room at Caesar's Palace, where most of "The Hangover" was shot.

"I grew up with my mom and two older sisters, and I was always trying to make them laugh, just like anybody. But I also had an appreciation for comics and people that understand comedy.

"I love the opportunities I've had. I mean, I've worked with Will Ferrell and Vince Vaughn and [Jerry] Stiller and now Zack [Galifinakis] and Bradley [Cooper], people who are naturally funny."

As for Phillips, he confessed that his humor comes from pain.

"I think all humor comes from pain. The more painful childhood you have the funnier, at least some people use it as a cover for pain they had as kids. Mine comes from pain," he said, reluctant to give details.

Phillips first got interested in directing through photography. "When I was younger I took a lot of pictures and it was kind of a natural progression, you start storytelling with photos.

"I actually started with documentary films because it was very linked with photography. And I just kind of went from there."

Though "going from there" is the hard part, Phillips said, his ascendance came through his early films and a fortuitous meeting.

"I'd made some documentary films, one went to Sundance. And I met [director-producer] Ivan Reitman through his son, Jason. Jason directed 'Up in the Air,' but he used to be an 18-year-old kid who made short films. And they were that good that he would go to Sundance," he recalled.

"I was there with a documentary that he had seen. I didn't know who Jason was and he went up to his dad and said, 'You gotta see this movie. This guy's really funny. I think you'll really like this.' And his dad came and saw it.

"I met Ivan through Jason, so I owe a lot of my whole thing to Jason, just introducing me to his dad. It's funny. Now Jason is one of the great filmmakers."

Ivan Reitman and his comic movies of the '80s had a profound influence on Phillips.

"They were the movies I grew up on. 'The Jerk' one of my favorite movies, 'Stripes,' one of my favorite movies. I love Preston Sturges. But as a kid I didn't know Preston Sturges. I found him later when I started studying film.

"But as a kid all you're watching is 'Revenge of the Nerds' and 'Stripes' and 'Blues Brothers,' so those guys, John Landis, Ivan Reitman, Carl Reiner who did 'The Jerk.' . . .

"I got to meet him a month ago and he loved 'The Hangover.' Loved it, like, was quoting it to me. It was so weird. He's like a legend," Phillips said.

"Everybody's influenced from the stuff of their past. But I think there have been people between me and all that stuff that have continued the legacy.

"I think we all just find the thing that kind of turns us on about filmmaking and that's the thing we lean towards."

Phillips is in such demand that he's finished "Due Date" with Robert Downey Jr. and will start the sequel to "The Hangover" next summer.

The sequel will not take place in Las Vegas, said Phillips.

"I think what people like about 'The Hangover' is not necessarily Vegas or the tiger or the baby.

"I think they like the characters, and I think what they like about 'Old School' is the characters, it doesn't have anything to do with the college or the fraternity.

"I think you could make a sequel to 'Wedding Crashers' and not have Vince [Vaughn] and Owen [Wilson] crashing weddings. They like those two guys in that movie. So the idea here is to take those characters and put them through a new set of paces."

Another indication of his clout is that he suffered no interference from producers or the studio when he made "The Hangover."

"I produced this, we were alone on this. We were pretty tight. On 'Road Trip,' Ivan Reitman produced it, and he really protected me from all that nonsense. I think I've been really lucky.

"And as I've gotten more successful, none of those people do interfere. They all think only YOU really know, so they let you go.

"I just finished a movie with Robert Downey and he would say to me, 'I feel like we're on a . . . student film. Where IS everybody?' because it's really small and there's no producers on the phones. There's nobody from the studio coming in.

"And Robert, who'd just come off 'Sherlock Holmes' and 'Iron Man,' which were massive shoots, he kept wondering if we were shooting a real movie."