2019-08-16 使用递归实现无限极分类

$dsn = "mysql:host=127.0.0.1;port=3306;charset=utf8;dbname=store";
$pdo = new PDO($dsn,'root','root');
//print_r($pdo);

function getTree($a=0,&$result=array(),$level=0){
    //使用global使$pdo在方法里可以被访问到
    global $pdo;
    //每次调用都让$level自增2
    $level+=2;
    //sql语句
    $sql = "select * from cate where parent_id ='$a'";
    $res = $pdo->query($sql);
    while($row = $res->fetch(PDO::FETCH_ASSOC)){
        //给名称加一个前缀 更容易让子类和父级分类区分开
        $row['name'] = str_repeat('***',$level).$row['name'];
        $result[]=$row;
        //再次调用自身
        getTree($row['cate_id'],$result,$level);
    }
    return $result;
}

function printcate(){
    $arr = getTree();
    $str = "<ul>";
    foreach($arr as $k=>$v){
        $str.="<li>".$v['name']."</li>";
    }
    $str.="</ul>";
    return $str;
}
echo printcate();