Re: unique random number

On Tue, 08 Aug 2000, you wrote: > Bas Verschaar wrote: > > Hi, > > > > Every time i create a page, i want a random number (0..9) to be > > generated but it may not be the same number as the previous number > > > > so: > > > > srand((double)microtime()*1000000); > > $number = rand(0,9); > > > > with this code sometimes the value of $number is the same as the > > previous number > > is it in some way possible to solve this problem without using a > > database? > > ... you could use some other "random numbers" like microtime, time, > hhost_adr ect. and calculate them into the number somehow. You could also > use a piece of the number you get from uniquid (see php-manual). By the nature of "random", you are allowing for the possibility that the same number comes up twice in a row. If it didn't, your system would not be truly random. You could solve this problem, I think, by passing the last number you generated to the script, and testing to see if the new random number is the same or not. If it is, then discard it, run the script again, and again and again until it's not the same. It's a bit un-elegant, and a bit brute force, but it should do it. It also incorporates the danger that the script will run forever, but if you calculate the probability, you'll discover it's very very small indeed. Of course, depending on how you're doing this, it may not be possible to use the above method. Regards, Richard