Posted by Kevin Williamson on 11/11/06 11:16

Thanks Jerry,

I'm not sure what version of PHP because I installed it on an intranet
and unless I visit the company do not have access to check.

I have had the guy send me the relevant file that contains the draw
sequence to have a look at. I think I'll use srand as a matter of course
and return the updated version...but I agree ... look suspect

thanks again

Kevin

Jerry Stuckle wrote:
> Kevin Williamson wrote:
>> Hi,
>>
>> I've written a lottery programme in PHP that selects 10 winners a week
>> from approximately 18,000 shares.
>>
>> The problem I have is that of the ten winners one week the same share
>> number was drawn the next week and an adjacent share number the
>> following week (that just happened to be owned by the same member)
>> The program is now being looked at suspisciously.
>>
>> The main core of the random draw simply puts all the current share
>> numbers into an array ($currWinner), draws a random number using the
>> rand function between 1 and the number of shares ($lottshares) and
>> returns the share id number.
>>
>> for the random element ofthe program I use:
>>
>> $currWinner = rand(1,$lottShares);
>>
>> is this random enough? or is it possible that it needs seeding
>> (although I don't totally understand seeding?
>>
>>
>> Any help will be appreciated.
>>
>> thanks
>> Kevin
>
> Kevin,
>
> Yes, I admit that does look suspicious! Of course, it's always possible
> for it to happen, but the when you're drawing 10 out of 18K are much
> against it :-)
>
> Which version of PHP are you running? The reason I asked, versions
> before 4.2 did not automatically seed the random number generator - you
> need to do it. See srand().
>
> Version 4.2 and later do this automatically if the generator hasn't been
> seeded.
>

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