Is the prayer of one who completes his prayer alone valid after the Imam and congregants have left the prayer due to the Imam laughing, and what is the ruling on one who leaves the prayer in this situation?

The prayer of an Imam who is overcome by laughter is invalid. As for one who is not overcome by it, he has committed a grave error and must seek forgiveness, and his prayer is invalid, as is the prayer of anyone who leaves with him. However, the prayer of the congregant is valid if he separates from the Imam due to an impurity or something similar. The Imam should be cautioned about two matters: habituating his son to avoid provoking him during prayer, and realizing the solemnity of standing before Allah the Almighty.