How to fetch data from PHP database and store in into JSON array?

i am getting one row at a time. (I am using REST API postman to see output)

    {  
   "error":false,
   "uid":"5af96e2e2d1000.15095126",
   "Generalnotice":{  
      "id":1,
      "headline":"N4",
      "link":"n4.in",
      "description":"n4 desc",
      "issued_at":"",
      "updated_at":null,
      "type":"general"
   }
}

but i want to fetch all the rows at once. i don't know where to put while loop. all internet tutorials are with mysql functions.

here is my code. let me make you understand the flow and my need. i am sending string request from android app to php which is i am receiving in fetchnotice.php file (line no - 4). then i am calling getGeneralNotice() function which is at another file DB_Funtions.php the request process in getGeneralNotice Function where i am fetching data from database and return in to FetchNotice.php. if i get any response then print it..

i am getting response. but only one row. i want all rows to Print. (No i am not using PDO)

fetchNotice.php

<?php
    require_once 'include/DB_Functions.php';
    $db = new DB_Functions();
    $response = array("error" => FALSE);
    if (isset($_POST['noticeType'])) {
        // receiving the post params
        $noticeType = $_POST['noticeType'];
       // getting the General Notices
       $Generalnotice = $db->getGeneralNotice($noticeType);
       if ($Generalnotice != false) {
           // General notice found
           $response["error"] = FALSE;
           $response["uid"] = $Generalnotice["unique_id"];
           $response["Generalnotice"]["id"] = $Generalnotice["id"];
           $response["Generalnotice"]["headline"] = $Generalnotice["headline"];
           $response["Generalnotice"]["link"] = $Generalnotice["link"];
           $response["Generalnotice"]["description"] = $Generalnotice["description"];
           $response["Generalnotice"]["issued_at"] = $Generalnotice["issued_at"];
           $response["Generalnotice"]["issued_at"] = $Generalnotice["role"];
           $response["Generalnotice"]["updated_at"] = $Generalnotice["updated_at"];
           $response["Generalnotice"]["type"] = $Generalnotice["type"];
           echo json_encode($response);
       }
       else {
           // user is not found with the credentials
           $response["error"] = TRUE;
           $response["error_msg"] = "Please try again!";
           echo json_encode($response);
       }
   }
   else {
       // required post params is missing
       $response["error"] = TRUE;
       $response["error_msg"] = "Required parameters are missing!";
       echo json_encode($response);
   }
?>

DB_Funtions.php

class DB_Functions {

private $conn;

function __construct() {
    require_once 'DB_Connect.php';
    // connecting to database
    $db = new Db_Connect();
    $this->conn = $db->connect();
}
    public function getGeneralNotice($noticeType) {
        $stmt = $this->conn->prepare("SELECT * FROM noticetable WHERE type = ?");
        $stmt->bind_param("s", $noticeType);
        if ($stmt->execute()) {
            $user = $stmt->get_result()->fetch_assoc();
            return $user;
            $stmt->close();
        } else {
            return NULL;
        }
    }
}