What is the best PHP library for generating Factur-X or XRechnung invoices?

No PHP library provides full EN 16931 Schematron validation out of the box. Libraries like horstoeko/zugferd generate CII XML but do not run Saxon-HE Schematron checks, which are required for legal compliance in France, Germany, and Belgium. The recommended approach for PHP is to call a self-hosted REST API (such as Factur-X Engine) via Guzzle or curl. The engine handles Saxon-HE, VeraPDF, and all profile-specific business rules internally.

How do I generate a Factur-X PDF from Symfony or Laravel?

Make a multipart POST request to /v1/convert with your base PDF and a JSON metadata string. In Symfony, use HttpClient::create()->request('POST', ...) with the body option set to a multipart array. In Laravel, use Http::attach('pdf', ...) followed by ->post(). The response body is a binary PDF/A-3 file ready to store or stream to the browser.

Can I validate Factur-X invoices from PHP before archiving them?

Yes. POST /v1/validate accepts a PDF or XML file and returns JSON with is_valid (boolean) and errors (array of Schematron rule violations). Use this as a pre-archiving gate in your PHP application to reject non-compliant supplier invoices before they enter your accounting system.

Tutorials / PHP

PHP Factur-X Library Alternative (API)

The robust alternative to fragile PHP Factur-X libraries. Handle strict E-Rechnung and Factur-X compliance in Symfony, Laravel, or WordPress without complex PDF or XML dependencies.

Prerequisites

PHP 8.1+
guzzlehttp/guzzle client

Full Implementation

post('http://localhost:8000/v1/convert', [
        'multipart' => [
            [
                'name'     => 'pdf',
                'contents' => fopen('input.pdf', 'r'),
                'filename' => 'input.pdf'
            ],
            [
                'name'     => 'metadata',
                'contents' => json_encode([
                    'invoice_number' => 'PHP-999',
                    'seller' => ['name' => 'PHP Solutions'],
                    'totals' => ['net_amount' => 120.50]
                ])
            ]
        ]
    ]);

    file_put_contents('factur-x-final.pdf', $response->getBody());
    echo "Success: File generated.";

} catch (\Exception $e) {
    echo "Error: " . $e->getMessage();
}
?>

PHP Libraries vs Docker API

Libraries like horstoeko/zugferd generate CII XML but skip the Schematron validation required for legal compliance. Libraries wrapping tcpdf or Ghostscript for PDF/A-3 embedding consume large amounts of RAM and break on edge cases. The Docker API approach isolates all complexity:

Approach	Schematron	Composer deps	PDF/A-3
horstoeko/zugferd	None	fpdf, dompdf, setasign	Partial
atgp/factur-x	None	smalot/pdfparser	Partial
Factur-X Engine API	Yes (Saxon-HE)	guzzlehttp/guzzle only	Yes (VeraPDF)

Use Case: Symfony Service with HttpClient

Use Symfony's native HttpClientInterface — no Guzzle required. Inject the service and call the engine from a Symfony command or event listener:

<?php
namespace App\Service;

use Symfony\Contracts\HttpClient\HttpClientInterface;

class InvoiceService
{
    public function __construct(
        private HttpClientInterface $http,
        private string $engineUrl = 'http://facturx-engine:8000'
    ) {}

    public function generateFacturX(string $pdfPath, array $metadata): string
    {
        $response = $this->http->request('POST', $this->engineUrl . '/v1/convert', [
            'body' => [
                'pdf'      => fopen($pdfPath, 'r'),
                'metadata' => json_encode($metadata),
            ],
        ]);

        if ($response->getStatusCode() !== 200) {
            throw new \RuntimeException('Engine error: ' . $response->getContent(false));
        }

        return $response->getContent(); // binary PDF string
    }
}

Use Case: Laravel Queued Job for Batch Generation

Dispatch invoice generation as a Laravel queued job after payment confirmation. Store the resulting PDF in S3 via Laravel's filesystem abstraction:

<?php
namespace App\Jobs;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Storage;

class GenerateFacturXInvoice implements ShouldQueue
{
    use Queueable;

    public function __construct(
        private int $orderId,
        private string $pdfPath,
        private array $metadata
    ) {}

    public function handle(): void
    {
        $response = Http::attach('pdf', file_get_contents($this->pdfPath), 'invoice.pdf')
            ->post(config('services.facturx.url') . '/v1/convert', [
                'metadata' => json_encode($this->metadata),
            ]);

        $response->throw(); // throws on 4xx/5xx

        Storage::disk('s3')->put(
            "invoices/{$this->orderId}.pdf",
            $response->body()
        );
    }
}

Use Case: Validate Supplier Invoices Before Archiving

When receiving e-invoices from suppliers via EDI or email attachment, validate compliance before injecting into your accounting system. Non-compliant invoices (broken VAT math, missing IBAN, wrong profile) are rejected with a structured error report:

<?php
use GuzzleHttp\Client;

function validateInvoice(string $filePath): array
{
    $client = new Client();
    $response = $client->post('http://localhost:8000/v1/validate', [
        'multipart' => [[
            'name'     => 'file',
            'contents' => fopen($filePath, 'r'),
            'filename' => basename($filePath),
        ]],
    ]);

    $result = json_decode($response->getBody(), true);

    if (!$result['is_valid']) {
        foreach ($result['errors'] as $error) {
            error_log("[{$error['code']}] {$error['message']}");
        }
        throw new \RuntimeException('Invoice failed EN 16931 validation');
    }

    return $result;
}

Frequently Asked Questions

Can I use plain `curl` instead of Guzzle?

Yes. PHP's native curl_setopt with CURLOPT_POSTFIELDS set to a multipart array works perfectly. The Guzzle example is shown for readability but any HTTP client that supports multipart/form-data works — including Symfony HttpClient and Laravel's Http facade.

How do I stream the PDF response to the browser in PHP?

Set the appropriate headers and echo the binary content: header('Content-Type: application/pdf'), header('Content-Disposition: attachment; filename="invoice.pdf"'), then echo $response->getBody(). In Laravel use return response($response->body(), 200, ['Content-Type' => 'application/pdf']).

Does the engine work with PHP running on shared hosting?

The Factur-X Engine Docker container runs separately from your PHP environment — it can be hosted on any VPS, cloud VM, or local server. Your PHP app on shared hosting simply makes HTTP requests to it. The engine requires at minimum 0.5 vCPU and 512 MB RAM on the host where it runs.