Question

Sorry if a solution exists anywhere else, but I couldn’t find one.

I have the following array:

$data = array(
    array('a', 'b', 'c'),
    array('e', 'f', 'g'),
    array('w', 'x', 'y', 'z'),
);

I am trying hard to write a function that will give an array like:

a
    e
        w
        x
        y
        z
    f
        w
        x
        y
        z
    g
        w
        x
        y
        z
b
    e
        w
        x
        y
        z
    f
        w
        x
        y
        z
    g
        w
        x
        y
        z
c
    e
        w
        x
        y
        z
    f
        w
        x
        y
        z
    g
        w
        x
        y
        z

The major problem here is that the number of source arrays and their lengths keep changing always. So a function should be capable of handling any data given to it.

I tried to come up with something like this:

function testfunc($data){
    $arrayDepth = count($data);
    foreach($data as $key=>$d){
        foreach($d as $e){
            echo $e . "\n";
            if($key < $arrayDepth){
                array_shift($data);
                testfunc($data);
            }
        }
    }
}

And the output I got was:

a
e
w
x
y
z
f
g
w
x
y
z
b
w
x
y
z
c
e
f
g
w
x
y
z

I am stuck for almost a day with no proper solution. Any help would be great! Thanks!

Answer 1

Recursion ^[Wikipedia] is your friend:

function product($arrays) {
    if(count($arrays) === 1) {
        return $arrays[0];
    }
    else {
        $result = array();
        foreach($arrays[0] as $value) {
            $result[$value] = product(array_slice($arrays, 1));
        }
        return $result;
    }
}

DEMO