login.php

<?php
session_start();
require_once('class.php');
if (isset($_POST['submit'])){
    if (empty($_POST['username']) || empty($_POST['password'])){
        echo "<p style='color:red'>Fill both fields</p>";
    }
    else{
        $user = new User();
        $username = $user->escapeInput($_POST['username']);
        $password = sha1($user->escapeInput($_POST['password']));
        if ($user->authenticate($username,$password)){
            $_SESSION['user'] = $username;
            header("Location:homepage.php");
        }
        else{
            echo "<p style='color:red'>Incorrect login details</p>";
        }
    }
}