返回嵌套数组的所有键

Question

given a nested array of arbitrary depth like this:

$array = array(
            1400=> 
                array(7300=>
                        array(
                            7301=> array(),
                            7302=> array(),
                            7305=> array(
                                7306=>array()
                            ),
                        ),
                    7314=>array()
                ),
            );

how would one get the hierarchy of keys for any key.

for example:

getkeys(7305);

should return 1400,7300,7305 in that order

or

getkeys(7314);

should return 1400,7314

all array keys are unique values

Answer 1

The idea is to check current array branch, and if the needle key isn't found, then iterate current items and check their array child nodes by recursive function calls. Before each step down we push a current key to stack, and pop the stack if the function does not found a needle key in whole branch. So if the key found, the function returns true by the chain, preserving successful keys in the stack.

function branchTraversing(& $branch, & $key_stack, $needle_key) {
  $found = false;
  if (!array_key_exists($needle_key, $branch)) {
    reset($branch);
    while (!$found && (list($key, $next_branch) = each($branch))) {
      if (is_array($next_branch)) {
        array_push($key_stack, $key);
        $found = branchTraversing($next_branch, $key_stack, $needle_key);
        if (!$found) {
          array_pop($key_stack);
        }
      }
    }
  } else {
    array_push($key_stack, $needle_key);
    $found = true;
  }

  return $found;
}

function getPath(& $array, $needle_key) {
  $path = [];
  branchTraversing($array, $path, $needle_key);
  return $path;
}

$test_keys = [1400, 7300, 7302, 7306, 7314, 666];

foreach ($test_keys as $search_key) {
  echo '<p>' . $search_key . ' => [ '
  . implode(', ', getPath($array, $search_key)) . ' ]</p>';
}