edit.php

<?php

require_once 'include/common.php';
require_once 'include/protect.php';

$errors = [
            isMissingOrEmpty ('title', $_POST['title']),
            isMissingOrEmpty ('isbn13', $_POST['isbn13']),
            isMissingOrEmpty ('price', $_POST['price']),
        ];

// remove all the empty elements
$errors = array_filter($errors);

if (!isEmpty($errors)) {
    $_SESSION['errors'] = $errors;

    include "edit-view.php";
    exit();
}  


$dao = new BookDAO();

$book = new Book();
$book->title = $_POST['title'];
$book->isbn13 =  $_POST['isbn13'];
$book->price = $_POST['price'];

$errors = array_merge($errors,checkError($book,["title","isbn13","price"]));

if (!isEmpty($errors)) {
    $_SESSION['errors'] = $errors;

    include "edit-view.php";
    exit();
}  

$dao->modify($book);


// send back to listing page
header("Location: list-view.php");
?>