If the array elements are unique, and are all integers or strings, here is a simple way to pick $n random *values* (not keys) from an array $array:
<?php array_rand(array_flip($array), $n); ?>
array_rand
(PHP 4, PHP 5, PHP 7)
array_rand — Pick one or more random keys out of an array
Descrierea
array_rand
( array
$array
[, int $num = 1
] ) : int|string|arrayPicks one or more random entries out of an array, and returns the key (or keys) of the random entries. It uses a pseudo random number generator that is not suitable for cryptographic purposes.
Parametri
-
array -
The input array.
-
num -
Specifies how many entries should be picked.
Valorile întoarse
When picking only one entry, array_rand() returns
the key for a random entry. Otherwise, an array of keys for the random
entries is returned. This is done so that random keys can be picked
from the array as well as random values. If multiple keys are returned,
they will be returned in the order they were present in the original array.
Trying to pick more elements
than there are in the array will result in an
E_WARNING level error, and NULL will be returned.
Istoricul schimbărilor
| Versiune | Descriere |
|---|---|
| 7.1.0 | The internal randomization algorithm has been changed to use the » Mersenne Twister Random Number Generator instead of the libc rand function. |
Exemple
Example #1 array_rand() example
<?php
$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$rand_keys = array_rand($input, 2);
echo $input[$rand_keys[0]] . "\n";
echo $input[$rand_keys[1]] . "\n";
?>
add a note
User Contributed Notes 4 notes
Anonymous ¶
14 years ago
Anonymous ¶
11 years ago
It doesn't explicitly say it in the documentation, but PHP won't pick the same key twice in one call.
grzeniufication ¶
6 years ago
<?php
/**
* Wraps array_rand call with additional checks
*
* TLDR; not so radom as you'd wish.
*
* NOTICE: the closer you get to the input arrays length, for the n parameter, the output gets less random.
* e.g.: array_random($a, count($a)) == $a will yield true
* This, most certainly, has to do with the method used for making the array random (see other comments).
*
* @throws OutOfBoundsException – if n less than one or exceeds size of input array
*
* @param array $array – array to randomize
* @param int $n – how many elements to return
* @return array
*/
function array_random(array $array, int $n = 1): array
{
if ($n < 1 || $n > count($array)) {
throw new OutOfBoundsException();
}
return ($n !== 1)
? array_values(array_intersect_key($array, array_flip(array_rand($array, $n))))
: array($array[array_rand($array)]);
}
grzeniufication ¶
6 years ago
<?php
// An example how to fetch multiple values from array_rand
$a = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g' ];
$n = 3;
// If you want to fetch multiple values you can try this:
print_r( array_intersect_key( $a, array_flip( array_rand( $a, $n ) ) ) );
// If you want to re-index keys wrap the call in 'array_values':
print_r( array_values( array_intersect_key( $a, array_flip( array_rand( $a, $n ) ) ) ) );
