Electronic invoicing with PHP

This tutorial builds two simple PHP applications from scratch:

Receive: connects and authenticates with the Invoicetronic API and downloads any new incoming invoices.
Send: connects and authenticates with the Invoicetronic API and sends an invoice to the SDI.

Before continuing, make sure all the prerequisites below are met.

Prerequisites

We assume that these prerequisites are met:

PHP 7.4+ or PHP 8.x has been downloaded and installed
Composer has been installed
You obtained an active API Key
You registered with the Italian Revenue Service (needed for the live environment)

We use Composer for dependency management, which is the de facto standard for modern PHP.

Tip

For an optimal PHP experience, consider using VS Code with the PHP extension or PHPStorm for a complete IDE.

Did you know?

The PHP SDK supports both Guzzle and other PSR-18 compatible HTTP clients, giving you flexibility in your implementation.

Receive

Create the app

The first step is to create the application directory:

mkdir receive && cd receive

Initialize the project with Composer:

composer init --name="invoicetronic/receive-example" --type=project --no-interaction

The command created a new PHP project with a composer.json file in the current directory.

Install the SDK

Install the Invoicetronic PHP SDK:

composer require invoicetronic/invoicetronic-sdk

Once that's done, open VS Code in the current directory:

code .

Configure the SDK

Create a new file called index.php and add the following code:

Configure the SDK

<?php
require_once(__DIR__ . '/vendor/autoload.php');

// Configure the SDK
$config = Invoicetronic\Configuration::getDefaultConfiguration()
    ->setUsername('YOUR TEST API KEY (starts with ik_test_)');

$config->setHost('https://api.invoicetronic.com/v1');

As you can see, we configure the SDK by setting the API's host and your test API Key (not the live one). Notice how we use the setUsername() method to set the API Key.

API Key comes in pairs

When you create your account, you obtain a pair of API Keys. One is the test key for the API Sandbox, and the other is the live API's. You can tell the difference because the former starts with ik_test_, while the latter begins with ik_live_. In this tutorial, always use the test key.

Download invoices

We are ready to make a request. We want to download new vendor invoices that may be available from the SDI. Add these lines:

Download unread invoices

// Download unread invoices
$receiveApi = new Invoicetronic\Api\ReceiveApi(
    new GuzzleHttp\Client(),
    $config
);

try {
    $inboundInvoices = $receiveApi->receiveGet(
        null,  // page
        null,  // pageSize
        null,  // sort
        true,  // unread
        true   // includePayload
    );

    echo "Received " . count($inboundInvoices) . " invoices\n";

    foreach ($inboundInvoices as $invoice) {
        if ($invoice->getEncoding() === 'Xml') {
            file_put_contents($invoice->getFileName(), $invoice->getPayload());
        } elseif ($invoice->getEncoding() === 'Base64') {
            file_put_contents($invoice->getFileName(), base64_decode($invoice->getPayload()));
        }

        echo "Downloaded {$invoice->getFileName()} from a vendor with VAT ID {$invoice->getPrestatore()}\n";
    }
} catch (Exception $e) {
    echo 'Error: ' . $e->getMessage() . "\n";
}

Payload Inclusion

We set includePayload: true to retrieve the actual invoice content in the payload property. Without this parameter, the payload field would be null by default, which increases performance and reduces response size when you only need metadata.

In the terminal, run the application:

php index.php

You should obtain an output similar to this one:

Received 3 invoices
Downloaded file1.xml from a vendor with VAT ID IT06157670966
Downloaded file2.xml.p7m from a vendor with VAT ID IT01280270057
Downloaded file3.xml.p7m from a vendor with VAT ID IT01280270057

The files are in the current directory, ready for you to inspect them.

Not receiving invoices in the live environment?

Ensure you registered with the Italian Revenue Service, which is a requirement for the live environment.

What we learned

In this example, we learned several things.

We must configure the SDK by calling getDefaultConfiguration() and setting the username (API key) with setUsername() and the host with setHost().
We must instantiate a class representing the endpoint we want to work with. In this case, we leverage ReceiveApi to download incoming invoices, passing an HTTP client (Guzzle) and the configuration.
Endpoint classes like ReceiveApi offer methods for interacting with their target entity. We call receiveGet() to retrieve invoices. Because we only want new, unread invoices, we pass true for the unread parameter. We also pass true for includePayload to retrieve the actual invoice content.
Invoice objects expose methods like getEncoding(), getFileName(), and getPayload(). The last one contains the invoice content, as plain text or Base64-encoded, as described by getEncoding().

Source Code on GitHub

The source code for this Quickstart is also available on GitHub.

Send

Create the app

The first step is to create the application directory:

mkdir send && cd send

Initialize the project with Composer:

composer init --name="invoicetronic/send-example" --type=project --no-interaction

Install the SDK

Install the Invoicetronic PHP SDK:

composer require invoicetronic/invoicetronic-sdk

Once that's done, open VS Code in the current directory:

code .

Configure the SDK

Create a new file called index.php and add the following code:

Configure the SDK

<?php
require_once(__DIR__ . '/vendor/autoload.php');

// Configure the SDK
$config = Invoicetronic\Configuration::getDefaultConfiguration()
    ->setUsername('YOUR TEST API KEY (starts with ik_test_)');

$config->setHost('https://api.invoicetronic.com/v1');

As you can see, we configure the SDK by setting the API's host and your test API Key (not the live one). Notice how we use the setUsername() method to set the API Key.

API Key comes in pairs

When you create your account, you obtain a pair of API Keys. One is the test key for the API Sandbox, and the other is the live API's. You can tell the difference because the former starts with ik_test_, while the latter begins with ik_live_. In this tutorial, always use the test key.

Send an invoice

We are ready to make a request. We want to send an invoice to the SDI. Add the following code:

Send an invoice

// Send an invoice
$filePath = '/some/file/path/filename.xml';

$metaData = [
    'internal_id' => '123',
    'created_with' => 'myapp',
    'some_other_custom_data' => 'value'
];

$sendApi = new Invoicetronic\Api\SendApi(
    new GuzzleHttp\Client(),
    $config
);

try {
    $sendData = new Invoicetronic\Model\Send();
    $sendData->setFileName(basename($filePath));
    $sendData->setPayload(file_get_contents($filePath));
    $sendData->setMetaData($metaData);

    $sentInvoice = $sendApi->sendPost($sendData);

    echo "The invoice was sent successfully, it now has the unique Id of {$sentInvoice->getId()}.\n";
} catch (Exception $e) {
    echo 'Error: ' . $e->getMessage() . "\n";
}

In the terminal, run the application:

php index.php

You should obtain an output similar to this one:

The invoice filename.xml was sent successfully, it now has the unique Id of 123.

What we learned

In this example, we learned several things.

We must configure the SDK by calling getDefaultConfiguration() and setting the username (API key) with setUsername() and the host with setHost().
We must instantiate a class representing the endpoint we want to work with. In this case, we leverage SendApi to send invoices. Endpoint classes like SendApi offer methods for interacting with their target entity. We call sendPost() to send an invoice.
The Send class exposes methods like setFileName(), setMetaData(), and setPayload(). The last one contains the invoice content, while setMetaData() is optional and binds custom data to the document.

Source Code on GitHub

The source code for this Quickstart is also available on GitHub.