07 Config

Goal

Make the database path configurable via an environment variable, and assemble the complete router.php. After this page you have the full runnable server.

Prerequisites

• Create Handler — all three handlers wired to the router

Environment Variable Config

Hardcoding 'items.db' in router.php means every environment — local dev, tests, production — shares the same file path. A single environment variable (ITEMS_DB) fixes that: the caller sets a path, the script falls back to items.db if the variable is absent.

$path = getenv('ITEMS_DB') ?: 'items.db';

getenv() returns false (not null) when a variable is unset — the ?: short ternary treats false the same as an empty string here, applying the default.

The Complete router.php

<?php
require_once __DIR__ . '/db.php';
require_once __DIR__ . '/handlers.php';

header('Content-Type: application/json');

$path = getenv('ITEMS_DB') ?: 'items.db';
$pdo = openDb($path);

$requestPath = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
$method = $_SERVER['REQUEST_METHOD'];

if ($method === 'GET' && $requestPath === '/items') {
    [$status, $body] = handleList($pdo);
} elseif ($method === 'GET' && preg_match('#^/items/(\d+)$#', $requestPath, $matches)) {
    [$status, $body] = handleGet($pdo, $matches[1]);
} elseif ($method === 'POST' && $requestPath === '/items') {
    $input = json_decode(file_get_contents('php://input'), true);
    [$status, $body] = handleCreate($pdo, $input);
} else {
    $status = 404;
    $body = ["error" => "not found"];
}

http_response_code($status);
echo json_encode($body);

From SQLite to MySQL — One Line

This tier's index named MySQL as an alternative target alongside SQLite. Because every query in store.php and db.php goes through PDO, switching databases only ever touches openDb's connection string — never the store or handler code:

// SQLite (what this tier builds)
$pdo = new PDO("sqlite:{$path}");

// MySQL — same PDO API, different DSN
$pdo = new PDO("mysql:host=localhost;dbname=items", $user, $pass);

The ? placeholder style used throughout store.php is portable across both drivers — no query changes needed. Building the MySQL-backed variant is left as follow-up work; the point of this page is that PDO is the abstraction that makes it a one-line change when you do.

Checkpoint

Run with a custom path:

ITEMS_DB=/tmp/x.db php -S localhost:8000 router.php

In a second terminal, hit any route (e.g. curl http://localhost:8000/items), then stop the server with Ctrl-C and verify the file was created at the custom path:

ls /tmp/x.db

Expected:

/tmp/x.db

Run without the variable to confirm the default:

php -S localhost:8000 router.php

A fresh items.db is created in the current directory on the first request.

Next

Continue to 08 Tests.