<?php
require_once("include/database.php");
if(isset($_POST['submit'])) {
    connect_bookstore(); // custom function
    $spassword = sha1($_POST['password']);
    $username = $_POST['username'];
    if ( checkpassword($username,$spassword) ) { //custom function
        header('Location:insert.php');
        exit;
    } else {
        $message = "Login failed!";
    }
}
?>

<?php
if (isset($message)) {
    echo $message;
}
?>

<?php
session_start();

require_once("include/database.php");
if(isset($_POST['submit'])) {
    connect_bookstore(); // custom function
    $spassword = sha1($_POST['password']);
    $username = $_POST['username'];
    if ( checkpassword($username,$spassword) ) { //custom function
        header('Location:insert.php');
        exit;
    } else {
        $_SESSION['message'] = "Login failed!";
        header('location: /yourfile.php');
        exit;
    }
}

if(isset($_SESSION['message']))
{
    echo $_SESSION['message'];
    unset($_SESSION['message']);
}
?>