php递归类别树连字符问题

Question

我有这段代码，它是具有多个选择的递归类别树；

我正在使用ezsql类，

$query = $db->get_results("SELECT * FROM categories");

function Cats($query, $mainid = 0)
{
    foreach($query as $category)
    {
        if($category->maincategoryid == $mainid)
        {
        echo '<option>';
        if($category->maincategoryid != 0){echo '-';}
        echo $category->categorytitle.'</option>';
        echo Cats($query,$category->categoryid);
        }
    }
}

echo '<select multiple>';
Cats($query);
echo '</select>';

我想像这样树，但连字符出现问题，连字符每个循环仅重复一次。

 Sites
    - Google
    -- Gmail
    -- Youtube
    - Yandex
    -- Mail
    -- Yandisk
    -- Maps
    Program
    - Graphic
    -- Adobe
    -- Corel Draw
    - Browser
    -- Internet Explorer
    -- Firefox
    -- Chrome

Answer 1

我已经对代码进行了一些调整，请尝试以下方法：

function Cats($query, $mainid = 0, $level = 0)
{
    foreach($query as $category)
    {
        if($category->maincategoryid == $mainid)
        {
            echo '<option>';
            if($category->maincategoryid != 0){echo str_repeat('-', $level);}
            echo $category->categorytitle;
            echo '</option>';
            echo Cats($query,$category->categoryid, ($category->maincategoryid === 0) ? 1 : ($level + 1));
        }
    }
}

echo '<select multiple>';
Cats($objects);
echo '</select>';