Select random array keys

Description

public Random\Randomizer::pickArrayKeys(array $array, int $num): array

Uniformly selects num distinct array keys of the input array.

Each key of the input array is equally likely to be returned.

Caution

The selection of the array keys depends on the internal structure of the input array. The returned array keys might be different for two equal input arrays and two Random\Engines with identical state, depending on how the input arrays have been created.

Parameters

array: The array whose array keys are selected.
num: The number of array keys to return; must be between 1 and the number of elements in array.

Return Values

An array containing num distinct array keys of array.

The returned array will be a list (array_is_list()). It will be a subset of the array returned by array_keys().

Errors/Exceptions

If num is less than 1 or greater than the number of elements in array, a ValueError will be thrown.
Any Throwables thrown by the Random\Engine::generate() method of the underlying Random\Randomizer::$engine.

Examples

Example #1 Random\Randomizer::pickArrayKeys() example

<?php
$r = new \Random\Randomizer();

$fruits = [ 'red' => '🍎', 'green' => '🥝', 'yellow' => '🍌', 'pink' => '🍑', 'purple' => '🍇' ];

// Pick 2 random array keys:
echo "Keys: ", implode(', ', $r->pickArrayKeys($fruits, 2)), "\n";

// Pick another 3:
echo "Keys: ", implode(', ', $r->pickArrayKeys($fruits, 3)), "\n";
?>

The above example will output something similar to:

Keys: yellow, purple
Keys: red, green, yellow

Example #2 Picking random values

<?php
$r = new \Random\Randomizer();

$fruits = [ 'red' => '🍎', 'green' => '🥝', 'yellow' => '🍌', 'pink' => '🍑', 'purple' => '🍇' ];

$keys = $r->pickArrayKeys($fruits, 2);
// Look up the values for the picked keys.
$selection = array_map(
    static fn ($key) => $fruits[$key],
    $keys
);

echo "Values: ", implode(', ', $selection), "\n";
?>