I went through this with two of my four children. Consistency is key when getting a child to stay in bed.
Here's what I did. Now this WILL get tiring, but it does work, usually within a few nights:
1. Pick his bed time and stick to it.
2. Sit him down and explain that there will be a new routine for bed and tell him what it is.
3. 20-30 minutes before bed time, tell him it's time to get ready for bed. Then, brush teeth, give a warm bath, put on p.j.'s, tuck into bed, read a story, say prayers , sing a soft "good night" song, kiss good night. All of this should be kept as quiet and peaceful as possible. (if he needs a "drink" before bed, remember to fit that in somewhere before tucking in.)
4. shut off light, close door, wait outside the door. (You can put in a night light if he's afraid of the dark.)
5. As SOON as he pops out of bed, go in, put him back into bed and say "it's time for sleep now, good night". NO hugs or kisses and no words other than "it's time for sleep now, good night" and leave the room, shut the door (repeat until he falls asleep). {If you kiss and hug, you're giving him what he wants and he now has incentive to carry on for hours and hours.}
Now this can get very ugly for a few nights. Crying, kicking, screaming are to be expected. Your resolve has to be strong. You must be ready for a power struggle. You might be at this for a couple of hours for the first few nights. There will most likely be tears and a fit or two or three...but after a few nights of complete consistency, he will get used to the routine and look forward to it.
Believe me, I felt like I was going to lose my mind for a while there, but it didn't take too long before they actually looked forward to bed time and it was a joy to put them to bed.