Randomly generated string seems to be the same if functions are called at very similar times

[eluser]rogierb[/eluser]
yeah, rand() uses the older libc library. mt_rand() uses a different (faster) algorithm based on the Mersenne Twister (mt).
It produces a better random number alhough anything generated by code is pseudo random.

Something like random.org provides true random number. There are more services out there like them