生成矩阵的所有组合

Question

I am using this code to generate all the combinations in a matrix but it is not returning output. Can you help me?

function combos($data, $all = array(), $group = array(), $val = null,$i=0) {
    if (isset($val)) {
        array_push($group, $val);
    }
    if ($i >= count($data)) {
        array_push($all, $group);
    } else {
        foreach ($data[$i] as $v) {
            combos($data, &$all, $group, $v, $i + 1);
        }
    }
    return $all;
}
$data = array(
    array('a', 'b'),
    array('d', 'e', 'g'),
    array('w', 'x', 'y', 'z')
);
$combos = combos($data);
print_r($combos);

the output should be

            0 1 2
array[0]  = a d w
array[1]  = a d x
array[2]  = a d y
array[3]  = a d z
array[4]  = a e w
array[5]  = a e x
array[6]  = a e y
.
.
.
array[23] = b g z

Answer 1

Pass $all as value and not as reference in your foreach loop. Also you are not collecting the returned value of combos function in your foreach loop.

Modify combos($data, &$all, $group, $v, $i + 1);
to
$all = combos($data, $all, $group, $v, $i + 1);