<?php

$conn = new mysqli('localhost', 'root', '', 'user');

if (mysqli_connect_errno()) {
printf("Connect failed: %sn", mysqli_connect_error());
exit();}

$uname = $_POST['uname'];
$psw = $_POST['psw'];
$options = [
'cost' => 12,];
$hashedpassword= password_hash($psw, PASSWORD_BCRYPT, $options);

$result = $mysqli->query("SELECT username FROM registration WHERE username = '$uname'");
$row_count = $result->num_rows; if($row_count == 1) {
echo 'User already exists, try another one.'; }
else {

$query = "INSERT INTO user (username, password) VALUES(?, ?)";
$statement = $mysqli->prepare($query);

$statement->bind_param('ss', $uname, $hashedpassword);

if($statement->execute())
{
     print 'Success! Last inserted record : ' .$statement->insert_id .'<br />';
}
else
{
     die('Error : ('. $mysqli->errno .') '. $mysqli->error);
}
$statement->close();