Generate unique combinations of PHP arrays

php_unique_array_combinations.php

<?php
/**
 * Generate unique combinations of an array...
 */
function combinations($array)
{
    $return = [];
    $num = count($array);
    // The total number of possible combinations
    $total = pow(2, $num);
    // Loop through each possible combination
    for ($i = 0; $i < $total; $i++) {
        //For each combination check if each bit is set
        $data = array();
        for ($j = 0; $j < $total; $j++) {
           // Is bit $j set in $i?
            if (pow(2, $j) & $i) {
                $data[] = $array[$j];
            }
        }
        if(count($data)) {
            array_push($return, $data);
        }
    }
    return $return;
}

/**
 * Generate numeric combinations as arrays e.g. [[3,2,1], [2,1], [2,3], [1,3],...]
 */
function numeric_combinations($count)
{
    $return = [];

    // The total number of possible combinations
    $total = pow(2, $count);
    // Loop through each possible combination
    for ($i = 0; $i < $total; $i++) {
        //For each combination check if each bit is set
        $data = array();
        for ($j = 0; $j < $total; $j++) {
           // Is bit $j set in $i?
            if (pow(2, $j) & $i) {
                $data[] = $j;
            }
        }
        if(count($data)) {
            array_push($return, $data);
        }
    }
    return $return;
}

$data = ['a','b','c'];
$combinations = numeric_combinations(count($data));
array_map(fn($combination) => array_map(fn($idx) => $data[$idx], $combination), $combinations);