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Php versions – Generating a series of sequential arrays of version-like values in PHP

I’ve been banging my head against this problem for a while. I feel like it should be simple, but I’m having a hard time coming up with a solution.

I’m looking to pre-populate a database, and I need to create SQL statements with some foreign key values. It would be tedious to hand-code them, so naturally I decided to do it in code.

What I want are series of arrays that have values as such:

[1]
[2]
[3]
[1,1]
[1,2]
[1,3]
[2,1]
[2,2]
...
[1,1,1]
[1,1,2]
[1,1,3]
...
[3,1,1]
...
[3,3,3]

I want to specify the number of values in the array, and the numerical value at which it causes the preceeding value to roll over.

In the example I gave above, it would be like generate(3,3), since the maximum number of elements is 3, and the highest value is 3.

How could I write some code that would give me this series of arrays?

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2

Answers


  1. 0

    This is a recursive function that will generate each of the combinations of the ranges up to the maximum value, with elements in each array from 1 to the number specified:

    function generate($elements, $maxvalue) {
    if ($elements == 0) return array();
    $result = array();
    foreach (range(1, $maxvalue) as $el) {
        $result[] = array($el);
    }
    foreach (range(1, $maxvalue) as $el) {
        foreach (generate($elements - 1, $maxvalue) as $arr) {
            $result[] = array($el, ...$arr);
        }
    }
    return $result;
}

$combs = generate(3, 3);

    Output is too long to show here but can be seen in this demo on 3v4l.org

    Note for PHP < 7.4, replace

    $result[] = array($el, ...$arr);

    with

    $result[] = array_merge(array($el), $arr);
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  2. 0

    Here’s a version using generators (which may be slightly easier on memory than pure arrays):

    function generate(int $elementsCount, int $maxValue, array $current = []): Generator
{
    for ($value = 1; $value <= $maxValue; $value++) {
        yield [...$current, $value];
    }
    if ($elementsCount > 1) {
        for ($value = 1; $value <= $maxValue; $value++) {
            yield from generate($elementsCount - 1, $maxValue, [...$current, $value]);
        }
    }
}

    Exemple usage + debug/print:

    $combinations = generate(3, 3);
print_r(iterator_to_array($combinations, false));

    Demo

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