How to call functions from PHP in javascript, Ajax not returning anything

I've been trying to get the data I have in my database(in my PHP file) over to my javascript program. I'm trying to get the query results over to the Javascript file so I can produce a graph out of these results.

I have tried to use ajax but it isn't responding anything back. I'm not sure where I'm going wrong. My PHP file is called MySQLDau.php. Any help is much appreciated! Thanks!

PHP code:

<?php

    header("Access-Control-Allow-Origin: *");

    //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 generateRoomID()
        {
            $sql = "INSERT INTO room (room_id) VALUES (null);";
            $result = $this->mysqli->query($sql);
            if ($result == true)
            {
                $toReturn["status"] = true;
                $toReturn["roomID"] = $this->mysqli->insert_id;
                return $toReturn;
            }
            else
            {
                $toReturn["status"] = false;
                $toReturn["message"] = mysql_error($this->mysqli);
                return $toReturn;
            }
        }

        public function saveRoom($data)
        {
            $roomID = $data[0];
            $roomDescription = $data[1];
            $columns = $data[2];
            $rows = $data[3];

            $this->mysqli->autocommit(FALSE);

            $this->mysqli->query("UPDATE room SET room_description='".$roomDescription."' WHERE room_id='".$roomID."';");

            for ($i = 0; $i<count($columns); $i++)
            {
                for ($j = 1; $j<=$rows[$i]; $j++)
                {
                    $currentLabel = "{$columns[$i]}{$j}";
                    $this->mysqli->query("INSERT INTO shelf (shelf_label) VALUES ('".$currentLabel."');");
                    $shelfID = $this->mysqli->insert_id;
                    $this->mysqli->query("INSERT INTO room_shelf (room_id, shelf_id) VALUES ('".$roomID."','".$shelfID."');");
                }
            }

            if ($this->mysqli->commit())
            {
                $toReturn["status"] = true;
                $toReturn["message"] = "Room Created";
                return $toReturn;
            }
            else
            {
                $this->mysqli->rollback();
                $toReturn["status"] = false;
                $toReturn["message"] = "SQL Error";
                return $toReturn;
            }
        }

        public function updateShelf($data)
        {
            $shelfID = $data[0];
            $itemName = $data[1];
        }

        public function getRoomDetails($data)
        {
            $roomID = $data[0];

            $sql = "SELECT room.room_description, shelf.shelf_label, shelf.shelf_id FROM room INNER JOIN room_shelf ON room.room_id=room_shelf.room_id INNER JOIN shelf ON shelf.shelf_id=room_shelf.shelf_id WHERE room.room_id='".$roomID."';";

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

            if (mysqli_num_rows($result) > 0)
            {
                $toReturn["status"] = true;
                $toReturn["message"] = "Room Found";
                $toReturn["room_description"] = $row['room_description'];
                $shelves = [];

                foreach ($result as $row)
                {
                    $currentShelf["shelf_label"] = $row['shelf_label'];
                    $currentShelf["shelf_id"] = $row['shelf_id'];
                    array_push($shelves, $currentShelf);
                }
                $toReturn["shelves"] = $shelves;
                return $toReturn;
            }
            else
            {
                $toReturn["status"] = false;
                $toReturn["title"] = "Error";
                $toReturn["message"] = "Room Not Found";
                return $toReturn;
            }

        }

        echo "Hello World!";

        public function getResults($data){

            $sql = "SELECT * FROM room";

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

            if (mysql_num_rows($result) == 1) {
                $obj = mysql_fetch_object($result, 'obResults');

            }

            echo json_encode($obj);
        }   
    }
?>

Part of my Javascript code:

  function callPHP() {
        $.ajax ({
            type: "GET",
            url: "MySQLDao.php",
            data: { action : 'getResults' },
            success: function(output) {
                alert(output);
            }
        });
    }