<?php

 $db = mysqli_connect('localhost','root','','users')
 or die('Error connecting to MySQL server.');

 $admin = 0;
 $username = $_POST['login'];
 $password = $_POST['pass'];

 $query = "INSERT INTO users(Admin, User, Password)
           VALUES('$admin', '$username', '$password')";


 if(!mysqli_query($db, $query))
 {
     echo 'wyjebalo sie';
 }