Uniqid每次返回相似的值

Question

I'm generating a 5 letter uniqid in PHP this way:

$id = substr(uniqid(),0,5);

And every single time I call it, I get the value 5004b. Why is that happening?

If I remove the substr, the 5004b part stays constant while the remaining changes. Isn't this severely reducing the entropy of the GUID being generated?

Answer 1

uniqid() is based on microtime(), the beginning is going to be the same for a long time.

My suggestion is that you just increment every time or something if you need a 5 digit long uniqid.