无法使用php codeigniter插入批量记录

有了这个数组，我试图使用insert\u batch将它插入表中

$arrayOfQuestions

包含多个数组，如下所示：

Array
(
    [0] => Array
        (
            [question_desc] => In human beings, partial pressure of carbon dioxide in the inspired and expired air is respectively
            [option_a] => 0.3 and 40 mm Hg
            [option_b] => 0.3 and 32 mm Hg
            [option_c] => 40 and 46 mm Hg
            [option_d] => 40 and 0.3 mm Hg
            [answer] => B
            [diff_level] => 4
            [solution] => Refer answer.
            [chapter_id] => 54
            [inst_id] => 1
            [subject_id] => 68
            [ref_q_id] => 8540371983
        )

    [1] => Array
        (
            [question_desc] => At high altitude, RBCs of human blood will
            [option_a] => Increase in number
            [option_b] => Decrease in number
            [option_c] => Decrease in size
            [option_d] => Increase in size
            [answer] => A
            [diff_level] => 2
            [solution] => At higher altitudes, due to low pressure of atmospheric oxygen, the body has to carry more oxygen than normal in per volume of blood to supply the body constantly. The increased number of RBC in blood ensures the presence of more haemoglobin and thus more oxygen is carried.
            [chapter_id] => 54
            [inst_id] => 1
            [subject_id] => 68
            [ref_q_id] => 8540371983
        )
)

我尝试了下面的代码，但数据没有插入到表中，因此返回true

$result = $this->db->insert_batch('test_temp_question', $arrayOfQuestions);

---

要成功为其插入数据，请执行以下操作：

if($result>0){
echo"successfull.";
}
else{
echo"not successfull";
}

---

insert\u batch

返回插入的行数或FALSE。$result的实际价值是多少？