Idioms about Laughing a lot:

Cracked me up---

Example: That joke was so funny that it "cracked me up."

Died laughing---

Example: That joke was so funny that I almost "died laughing."

Rolling in the aisles---

Example: The comedian was so funny that the audience was "rolling in the aisles."

"Laughed (my/your/his/etc.) head off"---

Example: She thought that his joke was so funny that she "laughed her head off."

"Laughed so loud that (my/your/his/etc.) sides were splitting"---

Example: I laughed so loud that my sides were splitting.