使用json将数据从sqlite发布到mysqldb

Question

我正在尝试通过Android应用程序发布JSON并将其解码为数组以将其存储在我的sqldb中。

我写了以下php代码。当我执行它时，它会显示[]（第6行）。

<?php
    include_once './db_functions.php';

    //Create Object for DB_Functions class
    $db = new DB_Functions(); 

    //Get JSON posted by Android Application
    $json = (isset($_POST["usersJSON"])? $_POST["usersJSON"] : '');

    //Remove Slashes    
    if (get_magic_quotes_gpc()){
        $json = stripslashes($json);
    }

    //Decode JSON into an Array
    $data = json_decode($json);

    //Util arrays to create response JSON
    $a=array();
    $b=array();

    //Loop through an Array and insert data read from JSON into MySQL DB
    for($i=0; $i<count($data) ; $i++)
    {
        //Store User into MySQL DB
        $res = $db->storeUser($data[$i]->userId,$data[$i]->userName);
        //Based on insertion, create JSON response
        if($res){
            $b["id"] = $data[$i]->userId;
            $b["status"] = 'yes';
            array_push($a,$b);
        }else{
            $b["id"] = $data[$i]->userId;
            $b["status"] = 'no';
            array_push($a,$b);
        }
    }

    //Post JSON response back to Android Application
    echo json_encode($a);
 ?>