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Wait for a JavaScript-rendered form, then make it fillable in PHP with cURL extension

React, Vue and friends render forms after the initial HTML arrives — so a too-eager render captures a spinner where the form should be, and a pdf_forms pass finds zero controls to convert. The fix is two request parameters, no code changes on your site: "wait_until": "networkidle" holds the render until the page stops fetching, and delay adds a fixed settling pause after that.

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/apply",
    'format' => "pdf",
    'pdf_forms' => true,
    'wait_until' => "networkidle",
    'delay' => 500,
]);

$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('spa-form.pdf', $bytes);
echo ($headers['x-form-fields'] ?? '?') . " // 0 here usually means you rendered too early\n";

wait_until accepts four stages, in order of patience: commit (bytes started arriving), domcontentloaded, load (the default), and networkidle (no network requests for a quiet period — the right choice for SPAs that hydrate after load). delay is an extra wait in milliseconds after that stage is reached: use a few hundred ms for forms that animate in, or that fetch their field list from an API after mount.

The feedback loop is X-Form-Fields: if it comes back 0 on a page you know has a form, the form was not in the DOM yet (or it is inside an iframe, which is never converted). Bump delay, or check the form is rendered server-side. Raise timeout (navigation cap, ms) for genuinely slow apps rather than looping retries — a failed render is never charged, but it is slower than one patient render.

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`	0 on a form page = rendered before the form existed.
`X-Demo-Duration-Ms`	How long the render took (demo route).
`X-Cache`	Cached responses replay instantly.

Wait for a JavaScript-rendered form, then make it fillable in PHP with cURL extension

Notes for cURL extension

Response headers worth reading

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