He's having his hair cut.
We use the "causative verb" when we do not carry out an action ourselves, but are responsible for the action being performed.
Causative verbs can be similar in meaning to passive verbs.
List of causative verbs
The causative verbs "have", "get", "make" and "let" are followed by the base form of the verb(which is actually an infinitive without "to").
Meaning: To force to do
・Peter made her do her homework.
・The teacher made the students stay after class.
・My mother made me go to the doctor's.
・The kidnappers made the hostages write the letters.
・The captain had made the soldiers bury all the corpses.
・I was madeto clean my room when I was just a lad.
・I will be made to rewrite the test if my mark is poor.
・The teacher will make me rewrite the test if my mark is poor.
Meaning: Asking, Request
For GET and HAVE: usually used with professional services.
・I went to the bank to have (get) my cheque cashed.
・I had (got) my hair cut last Saturday.
・She had the car washed at the weekend.
・I'm going to have (get) my hair cut
・I had (got) my leg hurt in an accident
・He is having (getting) his house painted by the Morgan company
・I'll have (get) it done by tomorrow morning.
・Peter had (got) his house repaired after the tornado last year.
・The President had (got) his speech written by a very talented group of writers.
・He will have (get) a deck built next summer.
・I have had (got) my teeth cleaned regularly.
・I need to have (get) the car tuned up.
・I need (to have / get) the car tuned up.
Meaning: allow, permit
・John let me drive his new car.
・Will your parents let you go to the party?
・I don't know if my boss will let me take the day off.
・Please let me help you.
・Don't let them leave!
・Let the door be opened by you.
・Let me not be mistaken.
・Let your nails be cut.
・Let not my suggestions be ignored.
・Let these documents be signed.
"to convince to do something" or "to trick someone into doing something."
Get vs. Have
Sometimes "get someone to do something" is interchangeable with "have someone do something," but these expressions do not mean exactly the same thing.
・I got the mechanic to check my brakes.
At first the mechanic didn't think it was necessary, but I convinced him to check the brakes.
・I had the mechanic check my brakes.
I asked the mechanic to check the brakes.