Php 为什么不能先选择查询，然后再编辑查询

此web应用程序是一个包含成员数据的表，如果单击“编辑”，它将链接到已选择成员数据的编辑页面，因此应首先选择该页面

但是 为什么选择查询不能先写后写编辑查询。 我试图将选择部分代码移到上面，但当运行程序时，它无法编辑（不工作） 注：如果我像下面这样写，效果很好。但我想知道原因

public function editMember($id)
{
    //UPDATE 
    if($this->input->post("btn") != null)
    {
        $arr = array(   
                "name" => $this->input->post('member_name'),
                "email" => $this->input->post('email'),
                "tel" => $this->input->post('phone')
            );
            $this->db->where("id", $id);
            $this->db->update('member', $arr);
            redirect("member", "refresh");
            exit();
    }

    $sql = "SELECT * FROM member WHERE id = $id"; //SELECT
    $rs = $this->db->query($sql);

    if($rs->num_rows() == 0)  //check the exist of data
    {
        $result['fetch'] = array();
    }
    else
    {
        $data['fetch'] = $rs->row_array(); // just fetch one row
        return $data['fetch'];
    }
}

Try this code

public function editMember($id)
{
    $sql = "SELECT * FROM member WHERE id = $id"; //SELECT
    $rs = $this->db->query($sql);

    //UPDATE 
    if($this->input->post("btn") != null)
    {
        $arr = array(   
                "name" => $this->input->post('member_name'),
                "email" => $this->input->post('email'),
                "tel" => $this->input->post('phone')
            );
            $this->db->where("id", $id);
            $this->db->update('member', $arr);
            redirect("member", "refresh");
            exit();
    }

    if($rs->num_rows() > 0)  //check the exist of data
    {
        $data['fetch'] = $rs->row_array(); // just fetch one row
    }


    $this->load->view('your_editpage.php',$data);
}