php - hash using sha512 - length of hash

Question

I'm creating a 'unique' string by using:

hash('sha512', uniqid());

Will this always be the same length of characters - 128?

Am I correct in thinking that if I wish to change this length I could use sha256. Is that the difference between sha256/512 - the length of the hash?

Answer 1

A SHA-512 is 512 bits long as the name indicates.
The difference between SHA-256 and 512 is primarily in the number of rounds they perform internally (and other small details).

Note that if your main concern is the length of the string you can use a base 64 representation, i.e. you can use this chars [A-Za-z0-9]