Unless its a McJob then your friend is probably retarded for letting himself get fired...
Businesses generally don't want legal hassle and assuming it simply isn't working out (rather than you've done something very silly like taking a dump on your boss's desk) then you negotiate an exit... you agree not to kick up a fuss as they get rid of you in return for them not officially sacking you but allowing you to resign and maybe even negotiating a future reference with you(depending on the situation/how much leverage you have).
How long ago did it happen, how it happened is important - your friend should probably talk to a solicitor who specialises in the area... see if he can resign instead. Otherwise he's potentially going to have some explaining to do at future interviews and could be caught out telling lies to future employers.
Businesses generally don't want legal hassle and assuming it simply isn't working out (rather than you've done something very silly like taking a dump on your boss's desk) then you negotiate an exit... you agree not to kick up a fuss as they get rid of you in return for them not officially sacking you but allowing you to resign and maybe even negotiating a future reference with you(depending on the situation/how much leverage you have).
How long ago did it happen, how it happened is important - your friend should probably talk to a solicitor who specialises in the area... see if he can resign instead. Otherwise he's potentially going to have some explaining to do at future interviews and could be caught out telling lies to future employers.