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Take a JPEG screenshot at a custom viewport size in PHP with cURL extension

Two independent knobs, one request: format picks the codec ("jpeg" here — much smaller files for photographic content), and width/height set the viewport the page believes it is being viewed in. 390×844 is an iPhone-class viewport, so responsive pages serve their mobile layout — media queries fire on viewport width, no user-agent tricks needed.

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/report/42",
    'format' => "jpeg",
    'width' => 390,
    'height' => 844,
]);

$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('mobile.jpg', $bytes);

When to pick which format: JPEG compresses gradients and photos far better and has no alpha channel; PNG is lossless and wins on flat UI, text and sharp edges. For mobile-layout QA screenshots at a fixed viewport, JPEG cuts transfer size dramatically with no visible cost. If you need the image to sit on a transparent background, that is PNG territory.

height here is the viewport height — what "above the fold" means for this render. Without full_page you get exactly that viewport; combine full_page: true with a width and the height is measured from the document instead, at which point the viewport height only affects lazy-load behaviour. All three parameters change the cache fingerprint, so a 390-wide render and a 1280-wide render are separate cache entries — as they should be.

Same endpoint, one more trick: if the page you are rendering has a form on it, adding "pdf_forms": true to a PDF render brings it back with real, fillable AcroForm fields — a PDF people can type into, not a picture of one. How that works.

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
`Content-Type`	image/jpeg for this request.
`X-Cache`	Each distinct width/height/format is its own cache entry.

Full parameter reference: the docs. Hard numbers on caps and timeouts: limits.

Take a JPEG screenshot at a custom viewport size in PHP with cURL extension

Notes for cURL extension

Response headers worth reading

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