帝国CMS 循环赋值到变量~【后台处理函数】自定义php函数

Question

function add_l_x($mid,$f,$isadd,$isq,$value,$cs){
    global $empire,$dbtbpre,$public_r,$class_r;
    $k = $_POST['k'];
    $sql=$empire->query("select * from {$dbtbpre}ecms_xx where k like '$k%' order by zs asc,qz desc limit 10");
    while($r=$empire->fetch($sql))
    {
        $value .= $r['title'];
    }
    
    return $value;

只能输出1条数据，while怎样赋值到变量输出,请求指导