ZUGFERD via PHP and JS API

<?php
    $token = 'YOUR_TOKEN'; // API-Token
    $apiUrl = 'https://konverter.zugferd-rechnungen.de/api/pdf2zugferd.php';

    $inputFile = 'invoice.pdf';
    $outputFile = 'ZUGFeRD_invoice.pdf';

    // Check input file
    if (!file_exists($inputFile)) {
            exit("❌ Error: The input file '{$inputFile}' was not found.\n");
    }

    $cfile = new CURLFile(realpath($inputFile), 'application/pdf', basename($inputFile));
    $postFields = [
        'file' => $cfile,
        'token' => $token,
        'dscheck' => 'yes', //Agree to transfer and data protection
        'desiredFilename' => $outputFile
    ];

    $ch = curl_init($apiUrl);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_HEADER, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postFields);

    $response = curl_exec($ch);
    $headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
    $body = substr($response, $headerSize);
    $contentType = curl_getinfo($ch, CURLINFO_CONTENT_TYPE);
    curl_close($ch);

    if (str_contains($contentType, 'application/pdf')) {
        file_put_contents($outputFile, $body);
        echo "✅ Stored: {$outputFile}\\n";
    } else {
        echo "❌ Error:\\n" . $body;
    }
?>

<form id="uploadForm">
        <input type="file" name="file" accept="application/pdf" required>
        <input type="text" name="desiredFilename" value="ZUGFeRD_invoice.pdf">
        <button type="submit">Upload</button>
    </form>

    <script>
    document.getElementById('uploadForm').addEventListener('submit', async function(e) {
        e.preventDefault();
        const form = e.target;
        const fileInput = form.file;
        const file = fileInput.files[0];

        if (!file) {
            alert('❌ Please select a pdf invoice.');
            return;
        }

        if (file.type !== 'application/pdf') {
            alert('❌ Only pdf files are allowed.');
            return;
        }

        const filename = form.desiredFilename.value || 'ZUGFeRD_invoice.pdf';

        const formData = new FormData();
        formData.append('file', file);
        formData.append('token', 'YOUR TOKEN');
        formData.append('dscheck', 'yes'); //Agree to transfer and data protection
        formData.append('desiredFilename', filename);

        try {
            const res = await fetch('https://konverter.zugferd-rechnungen.de/api/pdf2zugferd.php', {
                method: 'POST',
                body: formData
            });

            if (!res.ok || !res.headers.get('Content-Type')?.includes('application/pdf')) {
                const text = await res.text();
                throw new Error(text);
            }

            const blob = await res.blob();
            const url = URL.createObjectURL(blob);

            const a = document.createElement('a');
            a.href = url;
            a.download = filename;
            a.click();
            URL.revokeObjectURL(url);
        } catch (err) {
            alert('❌ Error during upload or conversion:\n' + err.message);
        }
    });
</script>