01 Why Persistence

Goal

Understand what the beginner tier's endpoint is missing and what this tier fixes. No code on this page.

Prerequisites

• Beginner — Serving JSON (the tier exit artifact)

What the Beginner Endpoint Can't Do

The beginner tier's router.php returns a hardcoded array:

$items = [
    new Item("Widget", 9.99),
    new Item("Gadget", 19.99),
    new Item("Gizmo", 29.99),
];

That array exists only for the lifetime of a single request — remember from the Introduction, every PHP request gets a fresh interpreter run with no state carried over. Two things make this a dead end for a real service:

1. No writes. There's no way to add, change, or remove an item through the API — the list is redeclared identically on every request.
2. No memory between requests. Even if you mutated $items mid-script, the next request starts from the same hardcoded array again. Nothing persists.

Every production CRUD API replaces this with a database for exactly these two reasons.

What This Tier Adds

You'll add a SQLite file (items.db) via PDO — PHP's built-in database abstraction layer — and a store class that wraps it. By the end of page 08 you'll have:

• GET /items — reads all rows from the database
• GET /items/{id} — reads one row by primary key
• POST /items — inserts a new row and returns it

The data survives across requests because SQLite writes it to disk. Tests use an in-memory SQLite connection (sqlite::memory:) so they stay fast and leave no files behind.

No Composer package needed for persistence itself — pdo_sqlite ships as a built-in PHP extension. Composer shows up on page 08, for PHPUnit.

Next

Continue to 02 Project Setup.