Broccoli has a shelf life in the fridge for up to 5 days.
After 5 days the broccoli will go bad and start growing bacteria on it which can make you sick if you eat it.
If you want to extend the life of the broccoli you can freeze the broccoli in freezer safe containers or freezer bags.
Or just put the broccoli in Ziploc bags and freeze it that way as well.
I freeze broccoli in regular Ziploc bags and when frozen the broccoli keeps for over a year without going bad.
The freezing temperatures keeps bad bacteria from growing on the broccoli which helps to extend the shelf life of the broccoli.
Bad broccoli will have mold on it, smell bad and start wilting as well as changing colors from the green to a brownish color.
If the broccoli is bad it should be thrown out to avoid getting you sick.