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 pushing used numbers onto an array) but there must be a quick way to do it.

any advice would be great.

Your method is probably fine. Using mt_rand() will speed things up a bit, though. — Bojangles
– Bojangles, Commented Oct 17, 2011 at 11:05

Sjoerd · Accepted Answer · 2011-10-17 11:05:50Z

10

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

answered Oct 17, 2011 at 11:05

Sjoerd

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1 Comment

Joey Ciechanowicz Over a year ago

Instead of the second 2 steps, use array_rand(array, 7)

George Cummins · Accepted Answer · 2011-10-17 11:05:20Z

5

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

answered Oct 17, 2011 at 11:05

George Cummins

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Comments

Yoshi · Accepted Answer · 2011-10-17 11:17:09Z

3

Simple one-liner:

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

answered Oct 17, 2011 at 11:17

Yoshi

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4 Comments

masoud Over a year ago

I voted up this, but generated array is not random enough, the sequence of elements is regular !

Yoshi Over a year ago

@Masoud M. Do you have any reference? (just out of curiosity)

masoud Over a year ago

Check this out. It generates like: Array( [0] => 2 [1] => 4 [2] => 5 [3] => 6 [4] => 7 [5] => 9 [6] => 10 )

Yoshi Over a year ago

Ah you mean the result is sorted? Yes, that may be true, but not a real problem. One could shuffle the input/output array to get an unsorted result.

Bjoern · Accepted Answer · 2011-10-17 11:06:33Z

0

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;
}

answered Oct 17, 2011 at 11:06

Bjoern

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1 Comment

Bjoern Over a year ago

Not very efficient, but easy to comprehend.

evan · Accepted Answer · 2011-10-17 11:20:30Z

0

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.

answered Oct 17, 2011 at 11:20

evan

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Comments

stonyau · Accepted Answer · 2016-01-05 10:22:08Z

0

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

answered Jan 5, 2016 at 10:22

stonyau

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