Answer:
to attach to a hollow core door you need what is known as a dry wall or gyp-rock anchor. all depending on what country you live in. these are made to screw into surfaces up to about 15 millimeters thick and hold into them.
Do yourself a favour and don'r bother trying to hang it. it would be a waist of otherwise good fittings. The best thing you can do with the door is to build a bonefire, but let let me know where you live because I'm freezing here in the U.K.