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Convert an HTML form to a fillable PDF in PHP with cURL extension

A plain URL-to-PDF render gives you a picture of a form — nice to look at, impossible to type into. Setting "pdf_forms": true (with "format": "pdf") changes what comes back: every supported control on the page becomes a real AcroForm field at its exact rendered position, and the PDF can be filled in with Adobe Acrobat, macOS Preview, a browser viewer or a phone reader, then saved with the values kept.

Below is a complete, runnable PHP program using cURL extension, no third-party dependency needed. It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

<?php
$body = json_encode([
    'url' => "https://your-app.com/intake-form",
    'format' => "pdf",
    'pdf_forms' => true,
]);

$ch = curl_init("https://snapdok.io/v1/render");
$headers = [];
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => $body,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_TIMEOUT => 90,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv('SNAPDOK_KEY'),
        'Content-Type: application/json',
    ],
    CURLOPT_HEADERFUNCTION => function ($ch, $line) use (&$headers) {
        $parts = explode(':', $line, 2);
        if (count($parts) === 2) $headers[strtolower(trim($parts[0]))] = trim($parts[1]);
        return strlen($line);
    },
]);

$bytes = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
curl_close($ch);

if ($status !== 200) {
    throw new RuntimeException("snapdok error $status: $bytes");
}
file_put_contents('fillable.pdf', $bytes);
echo ($headers['x-form-fields'] ?? '?') . " // AcroForm fields placed\n";

What converts: text-like <input>s (text, email, tel, date, password, number) become text fields — password renders masked and maxlength is enforced; <textarea> becomes a multiline field; checkboxes stay checkboxes; radio inputs sharing a name become a radio group with one choice across the group; <select> becomes a dropdown. Pre-filled values, readonly and checked state carry over.

What does not: file pickers, range sliders, color pickers, hidden or invisible inputs, forms inside iframes, and fake widgets built from styled divs. These are skipped cleanly and counted in X-Form-Skipped — never guessed at, never dropped in the wrong spot.

One layout consequence worth knowing before you file a bug: the forms path measures the page at paper width with print styles — the same geometry an ordinary PDF render uses — so the width parameter has no effect here, and a mobile-first page comes out in its paper layout, not its phone layout.

Notes for cURL extension

Plain ext-curl, no Composer needed. The details that bite: CURLOPT_RETURNTRANSFER must be set or the bytes are echoed to stdout instead of returned; the HTTP status has to be read explicitly with curl_getinfo() because cURL happily "succeeds" on a 401; and response headers need a CURLOPT_HEADERFUNCTION callback if you want to check things like X-Form-Fields. file_put_contents is binary-safe in PHP — strings are byte arrays — so no "b" flag dance is needed.

Response headers worth reading

Header	Meaning
`X-Form-Fields`	How many AcroForm fields were placed.
`X-Form-Skipped`	Controls skipped (unsupported or invisible).
`X-Cache`	HIT when served from the 24h cache — not charged.

Convert an HTML form to a fillable PDF in PHP with cURL extension

Notes for cURL extension

Response headers worth reading

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