Below is my sample code for my PHP program, and my database has already been created.
createteam.php:
<?php 
$response = array();
if($_SERVER['REQUEST_METHOD']=='POST'){
//getting values
$teamName = $_POST['name'];
$memberCount = $_POST['member'];
//including the db operation file
require_once '../includes/DbOperation.php';
$db = new DbOperation();
//inserting values 
if($db->createTeam($teamName,$memberCount)){
    $response['error']=false;
    $response['message']='Team added successfully';
}else{
    $response['error']=true;
    $response['message']='Could not add team';
}
}else{
$response['error']=true;
$response['message']='You are not authorized';
}
echo json_encode($response);
config.php:
<?php
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_HOST', 'localhost');
define('DB_NAME', 'iphone');
DbConnect.php:
<?php
class DbConnect
{
private $conn;
function __construct()
{
}
/**
 * Establishing database connection
 * @return database connection handler
 */
function connect()
{
    require_once 'Config.php';
    // Connecting to mysql database
    $this->conn = new mysqli(DB_HOST, DB_USERNAME, DB_PASSWORD, DB_NAME);
    // Check for database connection error
    if (mysqli_connect_errno()) {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }
    // returing connection resource
    return $this->conn;
}
}
DbOperation.php:
 <?php
 class DbOperation
 {
 private $conn;
 function __construct()
 {
    require_once dirname(__FILE__) . '/Config.php';
    require_once dirname(__FILE__) . '/DbConnect.php';
    // opening db connection
    $db = new DbConnect();
    $this->conn = $db->connect();
}
//Function to create a new user
public function createTeam($name, $memberCount)
{
    $stmt = $this->conn->prepare("INSERT INTO team(name, member) values(?, ?)");
    $stmt->bind_param("si", $name, $memberCount);
    $result = $stmt->execute();
    $stmt->close();
    if ($result) {
        return true;
    } else {
        return false;
    }
}
 }
However when I use HTTP POST method using Postman in Chrome, it states this
Notice: Undefined index: name in D:\xampp\htdocs\TestServ\api\createteam.php on line 9
Notice: Undefined index: member in D:\xampp\htdocs\TestServ\api\createteam.php on line 10
Warning: mysqli::__construct(): (HY000/1049): Unknown database 'iphone' in D:\xampp\htdocs\TestServ\includes\DbConnect.php on line 20 Failed to connect to MySQL: Unknown database 'iphone' Warning: mysqli::prepare(): Couldn't fetch mysqli in D:\xampp\htdocs\TestServ\includes\DbOperation.php on line 20
Fatal error: Uncaught Error: Call to a member function bind_param() on null in D:\xampp\htdocs\TestServ\includes\DbOperation.php:21 Stack trace: #0 D:\xampp\htdocs\TestServ\api\createteam.php(18): DbOperation->createTeam(NULL, NULL) #1 {main} thrown in D:\xampp\htdocs\TestServ\includes\DbOperation.php on line 21
What does this mean, and what should I change?
 
     
     
    