Really silly question but, can he read?

My 4 year old is in preschool and has been able to write his name for a while (Kendrick). I have noticed that for the pst couple of weeks he has been using the letters from fridge phonics to spell out words (go, no, stop, fish, milk, leaf, Nolan, Mekhi (his brothers), jar, etc.) When we are at the grocery store he is constantly asking, "What does D-E-L-I mean? " "What does A-I-S-L-E mean?" He has started trying to spell his name in lower case letters and can even write the names of some of his clmates and when the TV is on closed caption he can recognize certain words. My 11 year old could read by 4 and I am thinking that my 4 year old is ready. I know this is a weird question, but is he already reading or is he just memorizing things? If he is just memorizing how to spell things do you think he is ready to read.