SyntaxError: Unexpected end of JSON input at Object.parse (native) PHP MySQL

I am trying to display Data in MySQL DB. But, I keep getting SyntaxError: Unexpected end of JSON input at Object.parse (native) .

My PHP file which fetch the data is

<?php 
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8"); 

include_once 'config/database.php'; 
include_once 'objects/ideas.php'; 

$database = new Database(); 
$db = $database->getConnection();

$ideas = new ideas($db);

$stmt = $ideas->readAll();
$num = $stmt->rowCount();

if($num>0){

    $data="";
    $x=1;


    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)){
        // extract row
        // this will make $row['name'] to
        // just $name only
        extract($row);

        $data .= '{';
            $data .= '"id":"'  . $id . '",';
            $data .= '"name":"' . $name . '",';
            $data .= '"description":"' . html_entity_decode($description) . '",';
            $data .= '"SubmitedBy":"' . $SubmitedBy  . '",';
        $data .= '}'; 

        $data .= $x<$num ? ',' : ''; $x++; } 
} 

// json format output 
echo '{"records":[' . $data . ']}'; 
?>

My AngularJS Code,

 $scope.getAll = function() {
                $http.get("read_ideas.php").success(function(response) {
                    $scope.names = response.records;
                });
            }

And the Data in MySQL DB is just

id - 1
name - me
description - desc
SubmitedBy - me
created - 2016-05-19 14:13:10
modified - 2016-05-19 17:43:10

I am not able to figure out why it throws this error again and again.

i understand it is somehow not able to parse the data in db to JSON format. But, how can i fix it.