PHP Unique Random Numbers

Question

What would be a good way to generate 7 unique random numbers between 1 and 10. I can\'t have any duplicates. I could write a chunk of PHP to do this (using rand() and pushin

Answer 1

Populate an array with ten elements (the numbers one through ten), shuffle the array, and remove the first (or last) three elements.

Answer 2

Simple one-liner:

print_r(array_rand(array_fill(1, 10, true), 7));

Answer 3

Whole numbers? Well, if you want 7 out of 10 then you more efficiently DON'T want 3 out of 10.

Feel free to use any of the other responses but instead of creating 7 numbers start with 10 and eliminate 3. That will tend to speed things up by more than double.

Answer 4

• Create an array from 1 to 10 (range).
• Put it in random order (shuffle).
• Select 7 items from the array (array_slice)

Answer 5

The "shuffle" method has a MAJOR FALW. When the numbers are big, shuffle 3 billion indexs will instantly CAUSE 500 error. Here comes a best solution for really big numbers.

function getRandomNumbers($min, $max, $total) {
    $temp_arr = array();
    while(sizeof($temp_arr) < $total) $temp_arr[rand($min, $max)] = true;
    return $temp_arr;
}

Say I want to get 10 unique random numbers from 1 billion to 4 billion.

$random_numbers = getRandomNumbers(1000000000,4000000000,10);

PS: Execution time: 0.027 microseconds

Answer 6

Check out the comments in the php manual, there are several solutions for this.

An easy one is this one:

$min = 1;
$max = 10;
$total = 7;
$rand = array();
while (count($rand) < $total ) {
    $r = mt_rand($min,$max);
    if (!in_array($r,$rand)) $rand[] = $r;
}