In stitches
Definition 1 of 1
Pro Tip 1/3Context Matters
Used when someone finds something hysterically funny, often in a relaxed or informal situation. 
The play was so hilarious, I was in stitches the whole time!
Pro Tip 2/3Not Literal
It is a metaphorical expression and does not mean that someone is actually sewing stitches. 
His storytelling skills are so good, they always leave me in stitches.
Pro Tip 3/3Colloquial Humor
Often used to describe a humorous situation or joke that is understood and appreciated in a specific culture. 
You might not get why it's funny, but that joke has the locals in stitches.