在PHP中将数组重组为树结构

Question

I have an array like this one:

$array = array(
    array('id' => 'foo.bar'),
    array('id' => 'foo'),
    array('id' => 'foo.baz.bar'),
    array('id' => 'foo.bar.bar'),
);

I can split the id fields to get them as paths, and then I'd like to sort them into a tree... I tried this:

$result = array();

foreach($array as $element) {
    $path = explode('.', $element['id']);

    $subtree = $result;
    while(!empty($path)) {
        $path_element = array_shift($path);

        if(empty($path_element)) {
            $subtree['data'] = $element;
        } else {
            if(!is_array($subtree[$path_element])) {
                $subtree[$path_element] = array();
            }
            $subtree = $subtree[$path_element];
        }
    }
}

But all I get is a load of warnings and an empty $res-Array.

PHP Notice:  Undefined index: foo in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: bar in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: foo in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: foo in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: baz in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: bar in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: foo in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: bar in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0
PHP Notice:  Undefined index: bar in tree.php on line 24
PHP Stack trace:
PHP   1. {main}() tree.php:0

(Line 24 is $s = $s[$pe];)

Any hint?

EDIT: My desired output would be like this

$res = array(
  'foo' => array(
    'data' => ...
    'bar' => array(
      'data' => ...
      'bar' => array(
        'data' => ...
      ),
    ),
    'baz' => array(
      'bar' => array(
        'data' => ...
      ),
    ),
  ),
);

The data elements are the original elements from the array.

Answer 1

The code below generates the following result:

Array
(
    [foo] => Array
    (
        [data] => ...
        [baz] => Array
            (
                [bar] => Array
                    (
                        [data] => ...
                    )

        )

        [bar] => Array
        (
            [bar] => Array
            (
                [data] => ...
            )
        )
    )
)

I renamed some of you're variables...

$array = array(
    array('id' => 'foo.bar'),
    array('id' => 'foo'),
    array('id' => 'foo.baz.bar'),
    array('id' => 'foo.bar.bar'),
);


$res = array();

foreach($array as $e) {

    $parts = explode('.', $e['id']);

    $temp = &$res;

    foreach($parts as $key => $el) {
        if (!isset($temp[$el])) $temp[$el] = array();

        if ($key == count($parts)-1) $temp[$el] = array('data' =>  '...');
        $temp = &$temp[$el];
    }
}

print_r($res);