Not getting the JSON data in PHP - php

Question

I am creating an android application and submit the user details from Android application to php at server side by JSON. But at server side I am not getting the JSON data. At server side php the JSON comes from android application is seems null. I am using POST method for this. I know that my POST method code is wrong in PHP at server side. But I have no idea to solve this.
Here is my PHP code for getting JSON. Every time I get same message:
Required fields missing
Code:
<?php
/*
* Following code will create a new user row
* All user details are read from HTTP Post Request
*/
// array for JSON response
$response = array();
print_r($_POST);
// check for required fields
if (isset($_POST['Firstname']) && isset($_POST['Lastname']) && isset($_POST['Username']) && isset($_POST['Email']) && isset($_POST['Password']) && isset($_POST['Country']) && isset($_POST['Mobile'])) {
echo('bhargavi');
$Firstname = $_POST['Firstname'];
$Lastname = $_POST['Lastname'];
$Username = $_POST['Username'];
$Email = $_POST['Email'];
$Password = $_POST['Password'];
$Country = $_POST['Country'];
$Mobile = $_POST['Mobile'];
// include db connect class
require_once __DIR__ . '/db_connect.php';
// connecting to db
$db = new DB_CONNECT();
// mysql inserting a new row
$result = mysql_query("INSERT INTO users(Firstname,Lastname,Username,Email,Password,Country,Mobile) VALUES('$Firstname','$Lastname','$Username','$Email','$Password','$Country','$Mobile')");
// check if row inserted or not
if ($result) {
// successfully inserted into database
$response["success"] = 1;
$response["message"] = "User successfully Registered.";
// echoing JSON response
echo json_encode($response);
} else {
// failed to insert row
$response["success"] = 0;
$response["message"] = "Oops! An error occurred.";
// echoing JSON response
echo json_encode($response);
}
} else {
// required field is missing
$response["success"] = 0;
$response["message"] = "Required field(s) is missing";
// echoing JSON response
echo json_encode($response);
}
?>

Answer 1

Probably you should decode the json string before checking $_POST['Firstname'] etc...
Let's say you send from the app a string called data. On php you should do something like that:
$data = json_decode($_POST['data']);
and then check if $data contains the data you neeed by doing:
if (isset($data->Firstname) && isset($data->Lastname) etc...){
...
...
}
If I can give you an advice it would be better if you check data integrity directly from your app instead of doing it on your server, it would give the chance to spare some server resources...
As Jay Blanchard already mentioned don't use mysql like that or you'll be exposed to mysql injection...