条令只将一个结果保存到DB

我有这个代码，

foreach ($res_arr as $key => $value) {
    $post = array(
        'details_id'=>$key,
        'classsubject_id'=>$cs_id,
        'term'=>$term,
        'marks_obtained'=>$value,
        'remarks'=>''
    );
    $marks->fromArray($post);
    $marks->save();
     print_r($post);
}   

但它只向数据库中添加了一个结果，当我在循环中打印结果时，它正在打印这个数据

 Array
(
    [details_id] => 1
    [classsubject_id] => 10
    [term] => first
    [marks_obtained] => 23
    [remarks] => 
)
Array
(
    [details_id] => 6
    [classsubject_id] => 10
    [term] => first
    [marks_obtained] => 23
    [remarks] => 
)
Array
(
    [details_id] => 7
    [classsubject_id] => 10
    [term] => first
    [marks_obtained] => 23
    [remarks] =>

)

它只是将最后一个数组结果添加到数据库中帮我找个人