CODEWITHSUNDEEP
phparraysmultidimensional-arrayrandomarray-column
Jason Bale
Jason Bale

Reputation: 363

Select multiple random column values from a two-dimensional array

I want to select 5 random ID's from my array of rows. Here is my array $test:

$test = [
    ['id' => 13, 'pets' => 8],
    ['id' => 15, 'pets' => 8],
    ['id' => 16, 'pets' => 10],
    ['id' => 17, 'pets' => 9],
    ['id' => 18, 'pets' => 10],
    ['id' => 19, 'pets' => 10],
    ['id' => 20, 'pets' => 0],
    ['id' => 21, 'pets' => 8],
    ['id' => 22, 'pets' => 9],
    ['id' => 23, 'pets' => 4],
    ['id' => 24, 'pets' => 0],
    ['id' => 40, 'pets' => 8],
    ['id' => 43, 'pets' => 2],
];

How can I select 5 random ID's from the array and put them into a string like this:

$ids = '13,17,18,21,43';

I've tried to use array_rand(), but it does not seem to work for my type of array. I'm not sure if there are any other built in PHP functions that can do this type of job or if I have to create my own function. It would be nice to have my own function like this to plug in the number of required values.

Upvotes: 1

Views: 398

Answers (4)

mickmackusa
mickmackusa

Reputation: 47894

If you want random, unique ids in a random order, I recommend shuffling the array, then isolating upto 5 subarrays, then extracting the id values, then joining with commas. This way array_column() doesn't need to iterate the full array.

Code: (Demo)

shuffle($test);
echo implode(
         ',',
         array_column(
             array_slice($test, -5),
             'id'
         )
     );

If you want random, unique ids and don't mind that they will be in the same order as your input rows, then array_rand() can be used.

@AbraCadaver's approach works by applying temporary keys to the input array, picking five random keys, then joining with commas. Because the values inside the rows are never used, null can also be used as array_column()'s second parameter. These approaches should not be used if duplicate ids need to be honored. In other words, because id values are being applied to the first level keys, php will automatically destroy any rows with duplicated ids -- because a single level of an array cannot contain duplicate keys.

One way to avoid potentially destroying data is to call array_rand() on the original indexes of the input array, then filter those unique indexes by 5 randomly selected indexes. (Demo)

echo implode(
         ',',
         array_column(
             array_intersect_key(
                 $test,
                 array_flip(array_rand($test, 5))
             ),
             'id'
         )
     );

Finally, if you want 5 randomly selected, randomly ordered ids which may be selected more than once, then just make 5 iterated calls of array_rand(). (Demo)

for ($x = 0, $delim = ''; $x < 5; ++$x, $delim = ',') {
    echo $delim . $test[array_rand($test)]['id'];
}

Or (Demo)

echo implode(
         ',',
         array_map(
             fn() => $test[array_rand($test)]['id'],
             range(1, 5)
         )
     );

Upvotes: 0

AbraCadaver
AbraCadaver

Reputation: 78994

First extract the id column indexing also by the id, then pick 5 random ones, and finally implode into a comma separated list. Since keys must be unique, this has the added benefit of not returning duplicate ids if there happen to be duplicates in the array:

$ids = implode(',', array_rand(array_column($test, 'id', 'id'), 5));

For a function:

function array_rand_multi($array, $key, $num) {
    return implode(',', array_rand(array_column($array, $key, $key), $num));
}

Upvotes: 2

Andr&#233; DS
Andr&#233; DS

Reputation: 1901

You can proceed like this (short example) :

    <?php
        $items = array(
  array("id" => 43, "pets" =>2),
  array("id" => 40, "pets" =>8),
  array("id" => 24, "pets" =>0),
  array("id" => 23, "pets" =>4),
  );

       $ids = $items[array_rand($items)]["id"].",".$items[array_rand($items)]["id"].",".$items[array_rand($items)]["id"];
echo $ids;
        // Output Example : 24, 40, 23
    ?>

It will choose a random key from the main array ($items), example : 3, and output the "id" : 

$items[3]["id"]

for this example.

Here is a demo : http://sandbox.onlinephpfunctions.com/code/32787091e341cdf8e172d96b065b14b3ca834846

Upvotes: -1

Andreas
Andreas

Reputation: 23958

You can use array_column to only get the ID's and shuffle them.
Then use array_slice to get five items and implode.

$id = array_column($arr, "id");
Shuffle($id);
Echo implode(",", array_slice($id, 0, 5));

Upvotes: 4

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