Codeigniter MySQL 查询不起作用

我知道在控制器中进行查询不是很好的做法，但由于某种原因，它们在此控制器类中不起作用。我对编码点火器不太有经验，所以任何帮助都值得赞赏，因为我不知道如何设置它才能正常工作。我有一个获取信息的 ajax 脚本。

这是我的代码：

<?php
class Phonecall extends CI_Controller {
    public function index() {
        /*$con = mysqli_connect('localhost','root','root','MYDB');
        if (!$con) {
            die ('Could not connect: ' . mysqli_error($con));
        }*/
        //$operatorId = $_SESSION['Oper']['OperatorID']; //I also cannot figure out how to get $_SESSION information either
        //$sql = "SELECT phone_number FROM incoming_calls WHERE OperatorID='${operatorId}'";
        //$result = mysqli_query($con,$sql);
        $query = $this->db->query("SELECT phone_number FROM MYDB.incoming_calls");// WHERE OperatorID='${operatorId}'");
        while ($row = $query->row_array()) {
            $number = $row['phone_number'];
        }
        /*$sql = "SELECT Username, UserID, Name
            FROM tblUsers 
            WHERE PhoneHome='999-999-9999' OR PhoneCell='999-999-9999' OR PhoneWork='999-999-9999'";
        */
        $query = $this->db->query("SELECT Username, UserID, Name
            FROM MYDB.tblUsers 
            WHERE PhoneHome='999-999-9999' OR PhoneCell='999-999-9999' OR PhoneWork='999-999-9999'");
        while ($row = $query->row_array()) {
            $userArray[] = array("name" => $row['Name'], "username" => $row['Username'], "user_id" => $row['UserID']);
        }
        if (!empty($userArray)) {
            echo json_encode($userArray);
        }
        if (isset($_POST["drop"])) {
            $query = $this->db->query("DELETE FROM MYDB.incoming_calls 
                WHERE phone_number = $number
                LIMIT 1");
            if (!$result) {
                die ('Could not drop row: ');
            }
        }
        $this->db->close();
    }
}
?>

这是我的JS：

    var user = new Array();
    var user_id = new Array();
    var name = new Array();
    $.get(baseURL + 'phonecall/index', function(data) {//where baseURL is defined
        var loginInfo = jQuery.parseJSON(data);
        for (var i = 0; i < loginInfo.length; ++i) {
            name[i] = loginInfo[i].name;
            user[i] = loginInfo[i].username;
            user_id[i] = loginInfo[i].user_id;
        }
    }

我对框架了解不多，我正在尝试学习，我也不知道如何让这个文件访问 $_SESSION 数据。任何帮助将不胜感激。