This SitePoint series has explored REST principles. This article demonstrates building a RESTful web service using Slim, a PHP micro-framework inspired by Sinatra (Ruby). Slim's lightweight nature, with core components like routing, request/response handling, and minimal view support, makes it ideal for simple REST APIs.

Key Concepts:

• Slim is a PHP micro-framework perfect for straightforward RESTful services, supporting PHP 5.2 and both procedural and (5.3 ) functional programming styles.
• Routes map URIs to callback functions for specific HTTP methods. Slim efficiently handles multiple methods for the same URI.
• A library management application example showcases listing, adding, deleting, and updating book details via web service calls. NotORM, a lightweight PHP database library, handles database interaction.
• Endpoints use post(), put(), and delete() methods for creating, updating, and deleting book records respectively.

Introducing Slim:

Begin by downloading Slim. This example uses the 5.3 style. Create index.php:

<?php
require "Slim/Slim.php";

$app = new Slim();

$app->get("/", function () {
    echo "<h1>Hello Slim World</h1>";
});

$app->run();
?>

Accessing index.php in your browser displays "Hello Slim World". Slim autoloads necessary files. The Slim constructor accepts configuration (e.g., MODE, TEMPLATES.PATH, VIEW). MODE sets the environment (development/production), and TEMPLATES.PATH specifies the template directory. Custom view handlers can replace the default Slim_View. Example:

<?php
$app = new Slim(array(
    "MODE" => "development",
    "TEMPLATES.PATH" => "./templates"
));
?>

Route creation is crucial. Routes map URIs to callback functions based on HTTP methods. Slim prioritizes the first matching route; unmatched requests result in a 404 error. After defining routes, call run() to start the application.

Building a Library Service:

Let's create a library management service. NotORM simplifies database interaction (requires a PDO instance).

<?php
require "NotORM.php";

$pdo = new PDO($dsn, $username, $password); // Replace with your database credentials
$db = new NotORM($pdo);
?>

Listing Books:

This endpoint lists all books in JSON format:

<?php
// ... (previous code) ...

$app->get("/books", function () use ($app, $db) {
    $books = array();
    foreach ($db->books() as $book) {
        $books[] = array(
            "id" => $book["id"],
            "title" => $book["title"],
            "author" => $book["author"],
            "summary" => $book["summary"]
        );
    }
    $app->response()->header("Content-Type", "application/json");
    echo json_encode($books);
});
// ... (rest of the code) ...

get() handles GET requests. use allows accessing external variables within the anonymous function. The response header is set to application/json, and the book data is encoded as JSON.

Getting Book Details:

Retrieve a book by ID:

<?php
// ... (previous code) ...

$app->get("/book/:id", function ($id) use ($app, $db) {
    $app->response()->header("Content-Type", "application/json");
    $book = $db->books()->where("id", $id);
    if ($data = $book->fetch()) {
        echo json_encode(array(
            "id" => $data["id"],
            "title" => $data["title"],
            "author" => $data["author"],
            "summary" => $data["summary"]
        ));
    } else {
        echo json_encode(array(
            "status" => false,
            "message" => "Book ID $id does not exist"
        ));
    }
});
// ... (rest of the code) ...

The route parameter :id is passed to the callback function. Optional parameters use /book(/:id). For optional parameters without explicit callback arguments, use func_get_args().

Adding and Editing Books:

post() adds, and put() updates books:

<?php
require "Slim/Slim.php";

$app = new Slim();

$app->get("/", function () {
    echo "<h1>Hello Slim World</h1>";
});

$app->run();
?>

$app->request()->post() and $app->request()->put() retrieve POST and PUT data respectively. For browser-based PUT requests, use a hidden field _METHOD with value "PUT" in your form.

Deleting Books:

Delete a book by ID:

<?php
$app = new Slim(array(
    "MODE" => "development",
    "TEMPLATES.PATH" => "./templates"
));
?>

The delete() method removes the database record. The map() method handles multiple HTTP methods on a single route (not shown here).

Conclusion:

This article demonstrates building a basic RESTful web service with Slim. Further development should include robust error handling and input validation. The source code (not included here) can be found on GitHub (link not provided in original text). The FAQs section of the original text is omitted as it provides basic information readily available through Slim's documentation.

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