Generation of all possible combinations of array elements

combinations.php

<?php

function getIndexCombinations($arValues): array {
	$iProduct = 1;
	foreach ($arValues as $arSubArray) $iProduct *= count($arSubArray);

	$arIndexCombinations = [];

	for ($i = 0; $i < $iProduct; $i++) {
		$arIndices = [];
		$iCount = 1;
		for ($j = 0; $j < count($arValues); $j++) {
			$arIndices[$j] = ($i / $iCount) % count($arValues[$j]);
			$iCount *= count($arValues[$j]);
		}

		for ($j = 0; $j < count($arIndices); $j++) {
			$arIndexCombinations[$i][$j] = $arIndices[$j];
		}
	}

	return $arIndexCombinations;
}

// Example
$arValues = [['a','b'],[1,2,3],['A','B','C'],['I','K']];
$arCombinations = getIndexCombinations($arValues);

foreach ($arCombinations as $arLine) {
	foreach ($arLine as $iSubArrayId => $iIndex) {
		echo $arValues[$iSubArrayId][$iIndex];
	}
	echo PHP_EOL;
}

// If you have an associative array, you can change a bit code above, and gets the following function:
function getAssociativeIndexCombinations($arValues): array {
	$iProduct = 1;
	$arKeys = [];
	foreach ($arValues as $sKey => $arSubArray) {
		$iProduct *= count($arSubArray);
		$arKeys[] = $sKey;
	}

	$arIndexCombinations = [];

	for ($i = 0; $i < $iProduct; $i++) {
		$arIndices = [];
		$iCount = 1;
		for ($j = 0; $j < count($arValues); $j++) {
			$arIndices[$j] = ($i / $iCount) % count($arValues[$arKeys[$j]]);
			$iCount *= count($arValues[$arKeys[$j]]);
		}

		for ($j = 0; $j < count($arIndices); $j++) {
			$arIndexCombinations[$i][$arKeys[$j]] = $arIndices[$j];
		}
	}

	return $arIndexCombinations;
}

// Example
$arValues = ['10' => ['a','b'], '11' => [1,2,3], '12' => ['A','B','C'], '13' => ['I','K']];
$arCombinations = getAssociativeIndexCombinations($arValues);

$arKeys = array_keys($arValues);
foreach ($arCombinations as $arLine) {
	foreach ($arLine as $sKey => $iIndex) {
		echo $arValues[$sKey][$iIndex];
	}
	echo PHP_EOL;
}