<form action="inc/login.php" method="post">
                <div class="col s3">
                    <label for="username">Username</label>
                    <input name="username" type="text" class="validate">
                  </div>
                  <div class="col s3 login_link">
                    <label for="password">Password</label>
                    <input name="password" type="password" class="validate">
                  </div>
                  <div class="col s3 login_button">
                    <button class="btn waves-effect waves-light" type="submit" name="login">Submit
                      <i class="material-icons right">send</i>
                    </button>
                  </div>
                </div>
              </form>



<?php
    include "db.php";

    session_start();

    if(isset($_POST['login'])) {
        $username = $_POST['username'];
        $password = $_POST['password'];

        $username = mysqli_real_escape_string($connection, $username);
        $password = mysqli_real_escape_string($connection, $password);

        $query = "SELECT * FROM users WHERE username = '$username' ";
        $select_user = mysqli_query($connection, $query);

        if(!$select_user) {
             die("QUERY FAILED. " . mysqli_error($connection) . ' ' . mysqli_errno($connection));
        }

        while($row = mysqli_fetch_array($select_user)) {
            $db_id = $row['user_id'];
            $db_usename = $row['username'];
            $db_password = $row['user_password'];
            $db_firstname = $row['user_firstname'];
            $db_lastname = $row['user_lastname'];
            $db_role = $row['user_role'];
        }

        $password = crypt($password, $db_password);

        if($username === $db_usename && $password === $db_password && $db_role === 'admin') {
            $_SESSION['username'] = $db_usename;
            $_SESSION['firstname'] = $db_firstname;
            $_SESSION['lastname'] = $db_lastname;
            $_SESSION['role'] = $db_role;

            header("Location: ../admin");
        } else {
            header("Location: ../index.php");
        }
    }
?>