php - 在 PHP 中递归期间显示子类别并将类添加到列表

Question

我正在使用递归函数在 PHP 中显示类别和子类别。在MySQL数据库表中，有3列:

cat_id, parent_id, cat_name 

但是，我应该继续跟踪无序列表，以便添加类以使用 jQuery 制作下拉菜单。因此，HTML 代码应如下所示:

<ul>
    <li class = "dropdown"><a href = "#">Parent 1</a>
        <ul class = "sub-menu">
            <li><a href = "#">Sub 1</a></li>
            <li class = "dropdown">
                <a href = "#">Sub 2</a>
                <ul class = "sub-menu">
                    <li><a href = "#">Sub 2.1</a></li>
                    <li><a href = "#">Sub 2.2</a></li>
                    <li><a href = "#">Sub 2.3</a></li>
                </ul>
            </li>
            <li><a href = "#">Sub 3</a></li>
            <li><a href = "#">Sub 4</a></li>
            <li><a href = "#">Sub 5</a></li>
        </ul>
    </li>
    <li><a href = "#">Parent 2</a></li>
    <li><a href = "#">Parent 3</a></li>
    <li><a href = "#">Parent 4</a></li>
</ul>

我正在使用的递归函数:

$query = "select * from  categories";$result = $conn->query($query); $cats = array();while($cat = $result->fetch_assoc()){$cats_ID[$cat['cat_id']][] = $cat;$cats[$cat['parent_id']][$cat['cat_id']] = $cat;}

function build_tree($cats,$cat_id,$only_parent = false){
    if(is_array($cats) and isset($cats[$cat_id])){
        $tree = "<ul>\n";

        if($only_parent==false){
            foreach($cats[$cat_id] as $cat){
                $tree .= '<li><a href = "#">'.$cat['cat_name'];
                $tree .=  build_tree($cats,$cat['cat_id']);
                $tree .= "</a></li>\n";
            }
        }

        $tree .= "</ul>";        
    }
    else return null;

    return $tree;
}

我如何跟踪 ul 列表？

Answer 1

这应该像我在上面的评论中建议的那样通过添加 $深度 参数来实现。

$query = "select * from  categories";
$result = $conn->query($query);
$cats = array();
while($cat = $result->fetch_assoc()){
    $cats_ID[$cat['cat_id']][] = $cat;
    $cats[$cat['parent_id']][$cat['cat_id']] = $cat;
}

//added a depth argument that defaults to 1
function build_tree($cats,$cat_id,$only_parent = false, $depth=1){
    if(is_array($cats) and isset($cats[$cat_id])){
        //check if depth is > 1, output class, else, no class.
        if($depth > 1){
            $tree = "<ul class='sub-menu'>\n";
        } else {
            $tree = "<ul>\n";
        }

        if($only_parent==false){
            foreach($cats[$cat_id] as $cat){
                //get the recursion first
                //adjusted recursive call to include depth+1.
                $tmp =  build_tree($cats,$cat['cat_id'],$only_parent,$depth+1);

                //if we are at the first depth and there is child content
                if($depth == 1 && is_null($tmp)){
                    //add the dropdown class
                    $tree .= '<li class="dropdown"><a href = "#">'.$cat['cat_name'];
                } else {
                    //no dropdown class
                    $tree .= '<li><a href = "#">'.$cat['cat_name'];
                }
                //now append the recursion
                $tree .=  $tmp;
                $tree .= "</a></li>\n";
            }
        }
        $tree .= "</ul>";        
    }
    else return null;
    return $tree;
}

您应该能够用这个新函数替换您的函数，并且一切都应该正常工作，因为新添加的参数具有默认值。