my 9 year old son is afraid of the dark too. He has a nite light that plays music, so it distracts him a bit and it stays on all night. Also, it really helps if you put them to bed a lot earlier than you go to bed, that way they arent' as worried
Have there been any new happenings in his life? can you think of any reason he would start this, has he seen any scary movies or overheard scary stuff. Sometimes this is just a phase and will pass, how about school is all well there. It is best he stays in his own Bed ,possibly he says he is more afraid to be able to go into your Bed, Take him to his bed tell him its best if he stays there and leave, you could let him read for a while.If he comes to your room quietly tell him to go back., this will pass.