PHP无限分类（递归）

<?php 
// 测试数据
$rows=array(
        array(
            'id'=>'1',
            'name'=>'php技术',
            'pid'=>'0',
            'path'=>'0',
        ),
        array(
            'id'=>'2',
            'name'=>'linux技术',
            'pid'=>'0',
            'path'=>'0',
        ),
        array(
            'id'=>'3',
            'name'=>'Thinkphp',
            'pid'=>'1',
            'path'=>'0-1',
        ),
        array(
            'id'=>'4',
            'name'=>'系统安装',
            'pid'=>'2',
            'path'=>'0-2',
        ),
        array(
            'id'=>'5',
            'name'=>'文件上传',
            'pid'=>'3',
            'path'=>'0-1-3',
        ),
        array(
            'id'=>'6',
            'name'=>'硬盘分区',
            'pid'=>'4',
            'path'=>'0-2-4',
        ),
        array(
            'id'=>'7',
            'name'=>'软件安装',
            'pid'=>'4',
            'path'=>'0-2-4',
        ),
        array(
            'id'=>'8',
            'name'=>'JAVA技术',
            'pid'=>'0',
            'path'=>'0',
        ),
        array(
            'id'=>'9',
            'name'=>'分区格式化',
            'pid'=>'4',
            'path'=>'0-2-4-6',
        ),
        array(
            'id'=>'10',
            'name'=>'JAVA基础',
            'pid'=>'8',
            'path'=>'0-8',
        ),
    );

// 递归子级
function findchild(&$arr,$id){
    $childs=array();
    foreach ($arr as $key => $value) {
        if($value['pid']==$id){
            $childs[]=$value;
        }
    }
    return $childs;
}

// 查找当前级别的子级
function build_tree($root_id){
    global $rows;

    $childs=findchild($rows,$root_id);
    if(empty($childs)){
        return null;
    }
    foreach ($childs as $key => $value) {
        $rescurTree=build_tree($value['id']);
        if(null != $rescurTree){
            $childs[$key]['childs']=$rescurTree;
        }
    }
    return $childs;
}

$trees=build_tree(0);

echo "<pre>";
print_r($trees);
echo "</pre>";

function show($trees){
        $pre='';
        $str='';
        foreach ($trees as $tree) {
            if($tree['pid']>0){
                $pre='| '.str_repeat(' - ', substr_count($tree['path'],'-'));
            }
            $str.=$pre.$tree['name'].'<br/>';
            if(isset($tree['childs'])){
                $str.=show($tree['childs']);
            }
        }
        return $str;
    }
echo show($trees);
?>