PHP RecursiveIteratorIterator: Determining first and last item at each branch level

问题

I have extended Zend_View_Helper_Navigation_Menu, and it uses a RecursiveIteratorIterator to iterate over the menu tree. What I want to be able to determine is whether I am on the first or last item for a branch level in the tree.

Here's an example of what I'm looking for:

• Nav 1 (first)
  • Nav 1.1 (first & last)
    • Nav 1.1.1 (first)
    • Nav 1.1.2
    • Nav 1.1.3 (last)
• Nav 2
  • Nav 2.1 (first)
  • Nav 2.2 (last)
• Nav 3 (last)
  • Nav 3.1 (first)
  • Nav 3.2 (last)

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Additional Information

• PHP Version 5.2.13

---

Solution

Within the foreach ($iterator as $page) loop two variables can be used to keep track of the depths, $depth and $prevDepth. A simple comparison conditional can then determine the first item in a branch level: if ($depth > $prevDepth).

Creating a RecursiveCachingIterator using the Zend_Navigation_Container object and then using that to create the RecursiveIteratorIterator adds the the hasNext() method.

$rci = new RecursiveCachingIterator($container, CachingIterator::FULL_CACHE);
$iterator = new RecursiveIteratorIterator($rci,
                    RecursiveIteratorIterator::SELF_FIRST);
/* snip */
$prevDepth = -1;
foreach ($iterator as $page) {
    $depth = $iterator->getDepth();
    /* snip */
    if ($depth > $prevDepth) {
        // first branch item
    }
    /* snip */
    if (!$iterator->hasNext()) {
        // last branch item
    }
    /* snip */
    $prevDepth = $depth;
}

回答1:

Using RecursiveCachingIterator:

$rdi = new RecursiveDirectoryIterator('.');
$rci = new RecursiveCachingIterator($rdi, CachingIterator::FULL_CACHE); 
$rii = new RecursiveIteratorIterator($rci, RecursiveIteratorIterator::SELF_FIRST);

foreach ($rii as $file) {
    if ($file->isDir()) {
        echo $file->getFilename() . PHP_EOL;
    }
    elseif (!$rii->hasNext()) {
        echo $file->getFilename() . PHP_EOL;
    }
    elseif (count($rii->getCache()) == 1) {
        echo $file->getFilename() . PHP_EOL;
    }
}

Another solution with array:

function buildTree(RecursiveDirectoryIterator $iterator) {
    $tree = array();
    foreach ($iterator as $fileinfo) {
        if ($fileinfo->isDir()) {
            $tree[$fileinfo->getFilename()] = buildTree($iterator->getChildren());
        } else {
            $tree[$fileinfo->getFilename()] = $fileinfo->getFilename();
        }
    }
    return $tree;
}

function filterTree(array $tree) {
    foreach ($tree as $key => $value) {
        if (is_array($value)) {
            $tree[$key] = filterTree($value);
        } elseif (reset($tree) !== $value && end($tree) !== $value) {
            unset($tree[$key]);
        }
    }
    return $tree;
}

print_r(filterTree(buildTree(new RecursiveDirectoryIterator('.'))));

回答2:

If $iterator is a dense array, this might work:

// iterate container
$prevDepth = -1;
foreach ($iterator as $key => $page) {
    $depth = $iterator->getDepth();
    /* snip */
    if ($depth > $prevDepth) {
        // $page is first branch item

        if (isset($iterator[$key - 1])) {
            // $iterator[$key - 1] is last branch item in previous branch
        }
    }
    /* snip */
    $prevDepth = $depth;
}

You will have to test for the very last item separately.

来源：https://stackoverflow.com/questions/4348100/php-recursiveiteratoriterator-determining-first-and-last-item-at-each-branch-le