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 pushing used numbers onto an array) but there must be a quick way to do it.
any advice would be great.
Simple one-liner:
print_r(array_rand(array_fill(1, 10, true), 7)); Populate an array with ten elements (the numbers one through ten), shuffle the array, and remove the first (or last) three elements.
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; } 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.
An implementation of Sjoerd's answer:
$ar = range(1, 10); shuffle($ar); $ar = array_slice($ar, 0, 7); 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