php三种无限分类

无限分类，是指从一个最高分类开始，每个子分类都可以分出自己的若干个子分类，可以一直分下去，称为无限级分类；

下面是对省市县的无限极分类的列子。数据库如图：

代码示例如下：

function getTree1($data, $parent_id = 0)
{
    $tree = array();
    foreach ($data as $k => $v) {
        if ($v["parent_id"] == $parent_id) {
            unset($data[$k]);
            if (!empty($data)) {
                $children = getCategory($data, $v["id"]);
                if (!empty($children)) {
                    $v["_child"] = $children;
                }
            }
            $tree[] = $v;
        }
    }
    return $tree;
}



function getTree2($data, $parent_id = 0, $level = 0)
{
    static $tree = array();
    foreach ($data as $k => $v) {
        if ($v["parent_id"] == $parent_id) {
            $v["level"] = $level;
            $tree[] = $v;
            getTree($data, $v["id"], $level + 1);
        }
    }
    return $tree;
}



function getCrumbsBar($data, $id) {
    static $tree = array();
    foreach ($data as $k => $v) {
        if ($v["id"] == $id) {
            getCrumbsBar($data, $v["parent_id"]);
            $tree[] = $v;
        }
    }
    return $tree;
}