register.php

<?php
require_once('class.php');
if (isset($_POST['submit'])){
    if (empty($_POST['email']) || empty($_POST['username']) || empty($_POST['password1']) || empty($_POST['password'])){
        echo "<p style='color:red'>Fill all required fields</p>";
    }
    elseif ($_POST['password1'] != $_POST['password']) {
        echo "<p style='color:red'>Passwords do not match</p>";
    }
    else{
        if (strpos($_POST['email'],'.')  < 1 or strpos($_POST['email'],'@') < 1){
        echo "<p style='color:red'>Enter a valid email address</p>";
        }
        else{
            $user = new User();
            $email = $user->escapeInput($_POST['email']);
            $username = $user->escapeInput($_POST['username']);
            $password = sha1($user->escapeInput($_POST['password']));
            if ($user->register($email,$username,$password)){
                header("Location:login_html.php");
            }
        }
    }
}