Calling rand/mt_rand on forked children yields identical results

Question

I\'m writing a script that needs to execute concurrent tasks in PHP.

I ran a little test and ran into strange result. I\'m using pcntl_fork to generate a child. The

Answer 1

That is because all children start with the same state (fork() duplicates the code and data segments). And since rand and mt_rand are pseudorandom generators, they will all generate the same sequence.

You will have to re-initialize the random generator, for example with the process/thread ID or read a few bytes from /dev/urandom.