Post hoc fallacy and hasty generalization fallacy are similar in that they both involve jumping to conclusions. However, there is a difference between the two:
Post hoc fallacy is assuming a cause and effect relationship between two events, simply because one happened after the other.
Hasty generalization fallacy is drawing a general conclusion from a small sample or little evidence.
In other words, post hoc fallacy involves a leap to a causal claim; hasty generalization fallacy involves a leap to a general proposition.