Generate all the possible combinations of array elements

Question

I am trying to create a function generate all the possible unique combinations of array elements.

As an example, my array is $inputs = [1,2,3,4,5]; and I want to create all the possible combinations of a particular size $size = 3;.

So the result of the combinations should be like the result array.

$result = [
    [1,2,3],
    [1,2,4],
    [1,2,5],
    [1,3,4],
    [1,3,5],
    [1,4,5],
    [2,3,4],
    [2,3,5],
    [2,4,5],
    [3,4,5]
];

I created this following function.

function getCombinations(array $inputs, $size) {

    //$inputs = [1,2,3,4,5];
    //$size = 3;

    // if array length is equal to the input array size or size is larger than the array size
    // there is only one combination
    if (count($inputs) == $size || count($inputs) < $size) {
        return $inputs;
    }

    $result = [];

    $lastMostEndIndex = count($inputs) - 1;
    $lastMostStartIndex = $lastMostEndIndex - (count($inputs) - $size);
    $isHitLastMostEndIndex = false;

    $startIndex = 0;
    $endIndex = $size - 1;

    // runs until last most end index is reached
    while (!$isHitLastMostEndIndex) {

        $subArray = [];

        for ($i = $startIndex; $i <= $endIndex; $i++) {
            $subArray[] = $inputs[$i];
        }

        // pusing the combination to result array
        $result[] = $subArray;

        $startIndex++;
        $endIndex++;

        if ($endIndex > $lastMostEndIndex) {
            $isHitLastMostEndIndex = true;
        }
    }
    

    return $result;
}

But this function only returns

$result = [[1,2,3],[2,3,4],[3,4,5]];

I think I need to add more loops but I can not figure it out.

Can someone please give me a hand or point me how to get all the unique combinations out of this function?