Transform flat array into a hierarchical, multi-dimensional array

Question

I have a standard array with key-value pairs - and I want to use the keys to transform it into a multi-dimensional array. The difficulty seems to be that I need to loop recu

Answer 1

You could use references to successively iterate through and build up the nested array structure:

$out = array();
foreach ($arr as $key=>$val) {
    $r = & $out;
    foreach (explode(".", $key) as $key) {
        if (!isset($r[$key])) {
            $r[$key] = array();
        }
        $r = & $r[$key];
    }
    $r = $val;
}
return $out;