JSON_encode没有输出任何东西

Question

我想将一个php文件的查询结果发送到我的javascript，我使用了AJAX这似乎有效，因为它从我的BaseClass.php获取数据。但是，在使用JSON_encode时，它根本不会输出任何内容。因此，我无法解决如何将查询结果从一个php文件（MySQLDao.php）发送到我的BaseClass.php，以便我可以将其发送到我的Javascript文件。

我的代码：

BaseClass.php：

<?php

    error_reporting(E_ALL); ini_set('display_errors', 1);

    require("Conn.php");
    require("MySQLDao.php");

    //$param=$_REQUEST['action'];

    //echo json_encode($_GET);


    //echo var_dump(json_encode($_GET));


    $handle = fopen("php://input", "rb");
    $param = $_REQUEST['action'];
    while (!feof($handle)) {
        $param .= fread($handle, 8192);
    }
    fclose($handle);


    if (empty($param))
    {
        $returnValue["status"] = false;
        $returnValue["title"] = "Error";
        $returnValue["message"] = "No Data Recieved paige" .$param ."...";
        echo json_encode($returnValue);
        return;
    }
    else
    {
        $dao = new MySQLDao();
        if ($dao->openConnection() == false)
        {
            $returnValue["status"] = false;
            $returnValue["title"] = "Error";
            $returnValue["message"] = "Connection Could Not Be Established Between Server And Database";
            ob_clean();
            echo json_encode($returnValue);
        }
        else
        {
            //Decodes data, dont change
            $body = json_decode($param, true);
            $recieved = $body["data"];

            //Gets the result of a query
            $result = $dao->getResults($recieved);


        }
        $dao->closeConnection();

        //Return the result of the query
        ob_clean();


        echo json_encode("param" .$param); 
        echo json_encode("body" .$body);
        echo json_encode("recieved" .$recieved);
        echo json_encode("result" .$result);

        exit();



    }
?>

输出上述echo语句：

"paramgetResults""body""recieved""result"

MySQLDao.php - 此文件包含我想传递给我的js的查询结果

<?php

    error_reporting(E_ALL); ini_set('display_errors', 1);

    //Class for holding queries
    class MySQLDao
    {

        var $dbhost = null;
        var $dbuser = null;
        var $dbpass = null;
        var $mysqli = null;
        var $dbname = null;
        var $result = null;


        //constructor
        function __construct()
        {
            $this->dbhost = Conn::$dbhost;
            $this->dbuser = Conn::$dbuser;
            $this->dbpass = Conn::$dbpass;
            $this->dbname = Conn::$dbname;
        }

        //Attempt a connection to the database
        public function openConnection()
        {   

            //Try and connect to the database
            $this->mysqli = new mysqli($this->dbhost, $this->dbuser, $this->dbpass, $this->dbname);
            //If the connection threw an error, report it
            if (mysqli_connect_errno())
            {
                return false;
            }
            else
            {
                return true;
            }
        }

        //Get method for retrieving the database conection
        public function getConnection()
        {
            return $this->mysqli;
        }

        //Close the connection to the database
        public function closeConnection()
        {
            //If there is a connection to the database then close it
            if ($this->mysqli != null)
                $this->mysqli->close();
        }

        //-----------------------------------QUERY METHODS-------------------------------------

        public function getResults()
        {



            $sql = "SELECT room.room_description FROM room WHERE room.room_id = 1";

            $result = $this->mysqli->query($sql);


            //if (mysql_num_rows($result) == 1) {
            //  $obj = mysql_fetch_object($result, 'obResults');
            //  echo($obj);
            //  return $obj;
            //}

            echo json_encode($result);

            //echo($result);



            //return false;

        }


    }
?>

我的js文件中的AJAX代码：

$.ajax ({

        type: "GET",
        datatype: "application/json",
        url: "BaseClass.php",
        data: { action : 'getResults' },
        //error: function(err){console.log(err)},
        success: function(output) {

            console.log(output);
            //alert(output);
        }
        //error, function(err){console.log(err)}
    });

感谢任何帮助！