How can I generate the Cartesian product of multiple arrays in PHP while eliminating repetitions?

Calculating the Cartesian Product of Multiple Arrays in PHP

Problem:

Given multiple PHP arrays, how can we generate a Cartesian product that combines all possible combinations of elements from each array, excluding repetitions?

Solution:

To obtain a Cartesian product in PHP, we can define a recursive function called array_cartesian. This function takes an array of input arrays as arguments. The base case occurs when the number of arrays is zero, in which case an empty array inside an array is returned. Otherwise, the function uses the array_shift function to remove the first array from the list, and then recursively calls itself with the remaining arrays.

For each element v in the first array, the function iterates through each sub-array p in the Cartesian product of the remaining arrays. It then constructs a new sub-array by merging v with p, and adds this sub-array to the resulting Cartesian product.

Example:

Consider the following set of arrays:

$array[0][0] = 'apples';
$array[0][1] = 'pears';
$array[0][2] = 'oranges';

$array[1][0] = 'steve';
$array[1][1] = 'bob';

By passing these arrays to the array_cartesian function, we can obtain the Cartesian product:

$cross = array_cartesian(
    array('apples', 'pears',  'oranges'),
    array('steve', 'bob')
);

print_r($cross);

which produces the following output:

Array
(
    [0] => Array
        (
            [0] => apples
            [1] => steve
        )

    [1] => Array
        (
            [0] => apples
            [1] => bob
        )

    [2] => Array
        (
            [0] => pears
            [1] => steve
        )

    [3] => Array
        (
            [0] => pears
            [1] => bob
        )

    [4] => Array
        (
            [0] => oranges
            [1] => steve
        )

    [5] => Array
        (
            [0] => oranges
            [1] => bob
        )

)

Thus, the function effectively generates all unique combinations of elements from the input arrays.

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