Insert Json file int Mysql error: Undefined index

Hello all, please help in solving the next issue, I readed alot of posts but still didn't manage to fix it.
I have a json file and want to insert this file with php in a mysql table.
What I tried:
file dp.php:
<?
session_start();
$SERVER_NAME = "localhost";
$DB_LOGIN = "root";
$DB_PASS = "";
$DB_NAME = "terminals";
$db = mysql_pconnect ( $SERVER_NAME, $DB_LOGIN, $DB_PASS );
@mysql_query ( "SET NAMES `utf8`" );
mysql_select_db( $DB_NAME, $db );
@mysql_query ( "SET NAMES `utf8`" );
?>
file for inserting json file in mysql:
<?php
require('db.php');
// reading json file
$json = file_get_contents('terminals.json');
//converting json object to php associative array
$data = json_decode($json, true);
// processing the array of objects
foreach ($data as $user) {
$agent = $user['agent'];
$id = $user['id'];
$name = $user['name'];
$address = $user['address'];
$work_time = $user['work_time'];
$lat = $user['lat'];
$lng = $user['lng'];
$type = $user['type'];
$status = $user['status'];
}
//insert into mysql table
$sql = "INSERT INTO terminale(agent, id, name, address, work_time, lat, lng, type, status)
VALUES('$agent', '$id', '$name', '$address', '$work_time', '$lat', '$lng', '$type', '$status')";
?>
And the error what a recive in browser:
**Notice: Undefined index: address in C:\xampp\htdocs\TEST\Test_Map\json-mysql\json-mysql.php on line 12**
Please help with this.

 

Thank you Sail.
I/m a beginner in this, can you please help how to check based on my example?
Thank you

 

Ok Sail I see but what I have or need to with it?
--- Добавлено ---
I tried:
$address = array_key_exists('address', $user) ? $user['address'] : '';
if ($address)
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
and receive the answer: Key exists!
Notice: Undefined index: address in C:\xampp\htdocs\TEST\Test_Map\json-mysql\json-mysql.php on line 12

 

yes Sail, I'm using:"C:\xampp\htdocs\TEST\Test_Map\json-mysql\json-mysql.php" file
But if is possible to show in my code what to change. Thank you.