当使用echo-php数组包含mysql行时没有响应

当我尝试执行此操作时，没有响应：（回波线中的问题echo json_encode（$aMembers）；

我尝试在mysql控制台中执行查询，并运行它。。

<?php
header('Access-Control-Allow-Origin: *');
define('DATABASE_NAME', 'vtm2');
define('DATABASE_USER', 'root');
define('DATABASE_PASS', '');
define('DATABASE_HOST', 'localhost');
include_once('class.DBPDO.php');
$data = $_REQUEST["arr"];
Convert JSON string to Array
$someArray = json_decode($data , true);
$Vid_arr = explode(",", $someArray[0]);
$query_s =" select vtm_history.VId,vtm_history.uniqueId,vtm_history.latitude,vtm_history.longitude,vtm_history.course,vtm_history.speed,vtm_history.power,vtm_history.other,vtm_history.time from(SELECT tt.* FROM vtm_vehicle_unit tt INNER JOIN (SELECT Vid, MAX(time_stamp)  AS MaxDateTime FROM vtm_vehicle_unit GROUP BY Vid) groupedtt ON tt.Vid = groupedtt.Vid AND tt.time_stamp = groupedtt.MaxDateTime where valid = 1) valid_unit inner join vtm_history on valid_unit.Vid = vtm_history.VId where vtm_history.time >= valid_unit.time_stamp and vtm_history.VId in (";
 foreach( $Vid_arr as $elem){
            $query_s.=$elem.",";
        }
 $query_s = substr($query_s, 0, -1);
 $query_s.=")";
 if($someArray[1] == 1)
 {
    $query_s.=" and (vtm_history.time between '".$someArray[2]."' and '". $someArray[3]."' )";
echo $query_s;
 }
 else
 {
    $query_s.=" and vtm_history.time like '".$someArray[2]."'";
  echo $query_s;
 }
$DB = new DBPDO();
    $aMembers = $DB->fetchAll($query_s);

echo json_encode($aMembers);

?>