php · level 2 check

a guestbook stored in SQLite.

The village fete needs a guestbook on its website. Visitors send their name and a message. Your app checks each one, saves the good ones in an SQLite database, then shows the guestbook newest first, safely escaped, with a count at the top.

Each array in `$posts` stands in for one pretend `$_POST`. `clean_entry` trims and validates a form, throwing an `InvalidArgumentException` with a clear message when something is wrong. `save_entry` stores an entry using `prepare` and placeholders, and `show_entry` builds one escaped line of the guestbook.

Fill in each `____`, run it, and check every line. Then add a visitor of your own and run it again.

Your program

<?php
function clean_entry(array $form): array {
    $name = ____($form["name"] ?? "");
    $message = trim($form["message"] ____ "");
    if ($name === "" || strlen($name) > 20) {
        ____ new InvalidArgumentException("Name must be 1 to 20 characters.");
    }
    if (strlen($message) < 3) {
        throw new InvalidArgumentException("Message is too short.");
    }
    return ["name" => $name, "message" => $message];
}

function save_entry(PDO $db, array $entry): void {
    $insert = $db->____("INSERT INTO entries (name, message) VALUES (?, ?)");
    $insert->execute([____]);
}

function show_entry(array $row): string {
    return sprintf("%s wrote: %s", ____($row["name"]), ____($row["message"]));
}

$db = new PDO("sqlite::memory:");
$db->exec("CREATE TABLE entries (id INTEGER PRIMARY KEY, name TEXT, message TEXT)");

$posts = [
    ["name" => "Zoe", "message" => "Lovely garden party!"],
    ["name" => "", "message" => "Who am I?"],
    ["name" => "Omar", "message" => "<b>Best cake ever</b>"],
    ["name" => "Kit", "message" => "Hi"],
    ["name" => " Priya ", "message" => "See you next year."],
];

foreach ($posts as $form) {
    try {
        save_entry($db, clean_entry($form));
        echo "Thank you!\n";
    } catch (____ $e) {
        echo "Not saved: " . $e->____() . "\n";
    }
}

$rows = $db->query("SELECT name, message FROM entries ORDER BY id ____")->fetchAll(PDO::FETCH_ASSOC);
$total = count($rows);
echo "\nGuestbook: $total " . ($total === 1 ? "entry" : "entries") . "\n";
foreach ($rows as $row) {
    echo show_entry($row) . "\n";
}

Fill in every ____ then run the checks.

1 A good entry is saved and shownuses: databases
2 A blank name is turned awayuses: validation
3 A short message is turned awayuses: exceptions
4 HTML in a message is escapeduses: escaping
5 Newest first, with spaces trimmeduses: SQL
6 It counts the entriesuses: formatting

Take as long as you like and try as many times as you want.

a guestbook stored in SQLite.

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