ensuring diffrent random results

[Anon]

I've got a function that generates a random value in a given range and then uses that value to SELECT from a mySQL DB a record with the corresponding ID. This works fine.

But the problem is, I need to call this function 3 times in a row and have been having a problem with the same record being selected more than one time.

For instance, I would like this:

---

| 4 | 7 | 1 |

because there are no duplicates. But I am getting a Yahtzee...

---

| 4 | 4 | 4 |

About 1 in ten times. My random range is large enough this shouldn't be happening but one in 300 times.

Is there a way to seed the function differently (than the microtime()) that would ensure a more unique outcome?

Thanks...
-Alan

[Anon]

make sure you call srand() only once. my experience has been that the example in the php manual works fairly well.

I have done the same thing and noticed that I was getting duplicates (out of about 40 records total).

what I did to get around this was to add numbers to an array as they were used (you could tack them onto a delimited string, but I found this to be faster to implement)

if your array is zero, there are no duplicates, so just push that random onto the stack. If there are more than one, loop until you find one that isnt in the array.

note, that you need to have some sort of exception when the number of records in the database < number of random records to pull.

---

srand ((double) microtime() * 1000000);

if (sizeof($arrWinners)) {
while(in_array($iEntryNo, $arrWinners)) {
iEntryNo = rand(0,$iEntries - 1);
}
}
else {
$iEntryNo = rand(0,$iEntries - 1);
}
$arrWinners[] = $iEntryNo;