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Verify a fillable PDF render without opening the file in PHP with cURL extension

When form-PDF generation is part of a pipeline — nightly exports, CI checks, a queue worker — "did it actually come out fillable?" needs a machine answer, not a human opening Acrobat. snapdok puts the verification data in the response headers, so your code can assert on the render it just received.

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,
    'pdf_form_only' => 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('checked.pdf', $bytes);
echo ($headers['x-form-fields'] ?? '?') . " // assert on this in CI\n";

Three headers carry the contract. X-Form-Fields is the number of AcroForm fields placed — assert it equals the number of controls your form has, and you have a regression test that catches a broken deploy of your own form page, too. X-Form-Skipped counts controls that could not convert (file pickers, hidden inputs, iframe forms); a sudden rise means someone changed the form. X-Form-Extracted tells you whether pdf_form_only actually pruned the page or fell back to the full page — fallback is legitimate output, but your layout expectations may differ.

Two operational notes for pipelines: failed renders are never metered, and a repeat of an identical request inside 24 hours returns X-Cache: HIT and is also not charged — so a retrying job that occasionally double-fires does not eat quota. Rate limits surface as HTTP 429 with a Retry-After header; honour it instead of hammering.

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`	Fields placed — the number to assert on.
`X-Form-Skipped`	Unconvertible controls; watch for regressions.
`X-Form-Extracted`	Prune result when pdf_form_only was requested.
`Retry-After`	Present on 429 — seconds to back off.

Verify a fillable PDF render without opening the file in PHP with cURL extension

Notes for cURL extension

Response headers worth reading

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