Question

Let we explain what I mean.

Some time ago, while writing a program in c#, I’ve made following mistake:

int Randomize()
{
    Random r=new Random();
    return  r.Next(0,10);
}

in c#, this is a mistake, because, called several times in a row, this function will return the same value. This is because Random constructor uses time seed, and the time difference between calls was too low (took me an hour to find that one 🙂 ).

Now I’m using rand(...) in php, and I need for the output to always be different, even if 2 scripts are executed at the same time.

Do I have to do something to get this result, or is it designed to work this way?

Answer 1

the rand() and also mt_rand() calls srand() and mt_srand() to produce always random results.
But here’s an interesting post on php.net:

Note that the automatic seeding seems to be done with the current
number of seconds which means you can get the same results for several
runs on a fast server. Either call srand() yourself with a more
frequently changing seed or use mt_rand() which doesn’t appear to
suffer from the problem.

So, just call srand more frequently or mt_rand.