Adding a Branch to a Tree

<?php
function add_branch($tree, $branch){
    /*
    $tree is the pre-existing tree, and $branch is the branch that is to be added to the tree.
    */
    $temp = &$tree;
    foreach($branch as $node){
        if(array_key_exists($node, $temp)){
            $temp = &$temp[$node];
        }else{
            $temp[$node] = array();
            $temp = &$temp[$node];
        }
    }
    return $tree;
}

$tree = array();
$branch = array("1", "2", "3", "4", "5");
$tree = add_branch($tree, $branch);

$branch = array("1", "2", "5");
$tree = add_branch($tree, $branch);

print_r($tree);

/*this produces:
Array
(
    [1] => Array
        (
            [2] => Array
                (
                    [3] => Array
                        (
                            [4] => Array
                                (
                                    [5] => Array
                                        (
                                        )

                                )

                        )

                    [5] => Array
                        (
                        )

                )

        )

)
*/