validator.php

<?php
	require_once 'connect.php';
	$username = $_POST['username'];
	$password = $_POST['password'];
	$stmt = $conn->prepare("SELECT * FROM `user` WHERE username = '$username' && `password` = '$password'") or die(mysqli_error());
	if($stmt->execute()){
		$result = $stmt->get_result();
		$num_rows = $result->num_rows;
	}
	if($num_rows > 0){
		echo "Success";
	}else{
		echo "Error";
	}
?>