PHP combine two multi-dimensional arrays

Question

I am trying to use array_combine to combine two multi-dimensional arrays, but somehow not doing it correctly.

Here is array1:

Array(
    [Nov 18, 2         


        

Answer 1

array_merge_recursive gets you very close (your "key" is in index 1 of leaf arrays, and your value is in index 0). So do it in two steps: first get the merged array, then fiddle with the branches to get it right.

// This is a callback for array_map() which should have some more generic uses.
// array(array('k', 'v'), ...) -> array('k' => 'v', ...)
function flatten_branches($branches) {
    $newleaves = array();
    foreach ($branches as $leaf) {
        $newleaves[$leaf[0]] = $leaf[1];
    }
    return $newleaves;
}

function merge_flatten_branches($karray, $varray) {
    //$karray has the key-leaves, and $varray has the value-leaves
    $m1 = array_merge_recursive($karray, $varray);
    return array_map('flatten_branches', $m1);
}

$merged = merge_flatten_branches($array2, $array1);
print_r($merged);

Just for fun, here are two more approaches. Both of these are a bit slower than merge_flatten_branches, but illustrate some useful array concepts. (In other more functional-flavored languages than php, these might be preferred.)

function merge_flatten_branches_reduce($karray, $varray) {
    //$karray has the key-leaves, and $varray has the value-leaves
    $m1 = array_merge_recursive($karray, $varray);
    return array_map('flatten_branches_reduce', $m1);
}

function merge_flatten_branches_add($karray, $varray) {
    //$karray has the key-leaves, and $varray has the value-leaves
    $m1 = array_merge_recursive($karray, $varray);
    return array_map('flatten_branches_add', $m1);
}

// The functions below are callbacks for the two above.

function array_add($a1, $a2) {
    return $a1+$a2;
}

function flatten_leaf($leaf) {
    return array($leaf[0] => $leaf[1]);
}

function flatten_branches_add($branches) {
    $leaves = array_map('flatten_leaf', ($branches));
    $finalleaves = array();
    foreach ($leaves as $leaf) {
        $finalleaves += $leaf;
    }
    return $finalleaves;
}


function flatten_branches_reduce($branches) {
    $l = array_map('flatten_leaf', ($branches));
    return array_reduce($l, 'array_add', array());
}