I want to create a token generator that generates tokens that cannot be guessed by the user and that are still unique (to be used for password resets and confirmation codes).

I often see this code; does it make sense?

md5(uniqid(rand(), true));

According to a comment uniqid($prefix, $moreEntopy = true) yields

first 8 hex chars = Unixtime, last 5 hex chars = microseconds.

I don't know how the $prefix-parameter is handled..

So if you don't set the $moreEntopy flag to true, it gives a predictable outcome.

QUESTION: But if we use uniqid with $moreEntopy, what does hashing it with md5 buy us? Is it better than:

md5(mt_rand())