如何使用分层数据结构打印列表? [英] How to print list using hierarchical data structure?

问题描述

当我运行此代码时:

foreach ($tree as $node) {
    echo str_repeat(' ', $node->tree_depth * 4) . $node->id . PHP_EOL;
}

我得到格式正确的文本，例如:

I get well formatted text like:

Food
 Fruit
   Red
     Cherry
     Strawberry
               Cool
               Not cool
   Yellow
     Banana
 Meat
   Beef
   Pork

但是我想用<ul><li>...创建一个列表:

But I want to create a list with <ul><li>...:

我尝试过:

echo '<ul>';
$prev_depth = 0;
foreach($table->fetchTree() as $row) {
    if ($row->tree_depth > $prev_depth) {
        echo '<li><ul>';
    } else if ($row->tree_depth < $prev_depth) {
        echo '</li></ul>';
    }
    echo '<li>' . $row->name . '</li>';
    $prev_depth = $row->tree_depth;
}
echo '</ul>';

但是我还有一些额外的ul标签，依此类推.我在此上损失了2天，因此如果您可以帮助我，请在此处发布...

But I have some extra ul tags and so on. I lost 2 days on this so if you can help me please post here...

推荐答案

尝试以下算法:

$tree = array(
    array('Food', 0),
    array('Fruit', 1),
    array('Red', 2),
    array('Cherry', 3),
    array('Strawberry', 3),
    array('Cool', 4),
    array('Not cool', 4),
    array('Yellow', 2),
    array('Banana', 3),
    array('Meat', 0),
    array('Beef', 1),
    array('Pork', 1),
);

$depth = -1;
$flag = false;
foreach ($tree as $row) {
    while ($row[1] > $depth) {
        echo "<ul>\n", "<li>";
        $flag = false;
        $depth++;
    }
    while ($row[1] < $depth) {
        echo "</li>\n", "</ul>\n";
        $depth--;
    }
    if ($flag) {
        echo "</li>\n", "<li>";
        $flag = false;
    }
    echo $row[0];
    $flag = true;
}
while ($depth-- > -1) {
    echo "</li>\n", "</ul>\n";
}

在这里，您只需将$tree替换为$table->fetchTree()，将$row[0]替换为$row->name，将$row[1]替换为$row->tree_depth.

Here you just need to replace $tree by $table->fetchTree(), $row[0] by $row->name and $row[1] by $row->tree_depth.

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