How to repair the leg of a computer chair
Replacing is probably most practical.

But if you really want to fix it, you need something to support the weight.  Tape and glue aren't going to do it. I would find a length of strong pipe (check the plumbing section at a home improvement store) that will fit nicely either inside the leg (if it is hollow) or over top of it.  Make the pipe fill/cover as much of the leg as possible.  Then attach with tape, glue, bolts, whatever - just to stop it from sliding out.

If the pipe fits snugly it should hold up fairly well.