Sometime it is necessary to generate a list of different random numbers. A possible usage scenario therefore could be a raffle where the winners should be choosen by chance, but every single user shouldn’t get more than one prize.
So in the following snippet, I’ll show you how to generate a list of different randoms in PHP.
<?php
//Create an array of numbers from which the randoms
//should be choosen. (For raffle: the list of user id's)
$array = range($minimum, $maximum);
//Initialize the random generator
srand ((double)microtime()*1000000);
//A for-loop which selects every run a different random number
for($x = 0; $x < $numberOfRandoms; $x++)
{
//Generate a random number
$i = rand(1, count($array))-1;
//Take the random number as index for the array
$result[] = $array[$i];
//The chosen number will be removed from the array
//so it can't be taken another time
array_splice($array, $i, 1);
}
?>
Advice: $minimum, $maximum and $numberOfRandoms must be determined by you before.
Why do you calling the srand?
The function works without this line.
Can you explain please?
Great tutorial!! This tutorial was really helpful to create a random numbers. you just made my work easier.
Thanks.
Hi,
Here is a php function to get an array with unique random numbers.
// Function to get an array with unique random numbers. Receives 3 arguments
// $nri = number of items in array
// $min = the lowest number
// $max = the largest number
function randomNrsArray($nri, $min, $max, $arr=array()) {
// From: http://coursesweb.net/php-mysql/
$nr = mt_rand($min, $max); // gets a random number
// if the number already exists in $arr, autocalls this function
// else, adds the number in $arr
// if the number of items in $arr is lower then $nri, autocalls the function (till gets $nri elements in $arr)
// returns the array
if(in_array($nr, $arr)) $arr = randomNrsArray($nri, $min, $max, $arr);
else {
$arr[] = $nr;
if(count($arr) < $nri) $arr = randomNrsArray($nri, $min, $max, $arr);
}
return $arr;
}
// Usage, gets an array with 5 uynique random numbers, between 1 and 100
$nrs = randomNrsArray(5, 1, 100);
// Test
var_export($nrs);
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