How to retrieve files using Google Drive API v3 with PHP

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1

I need help figuring out how file retrieval works with Google Drive API v3 in PHP. Back when I used API v2, the process was straightforward. I would fetch the file details first, then use the downloadUrl field to get a direct download link. After adding my oAuth token to that URL, I could make a simple GET request.

Now with API v3, that method doesn’t work anymore. The documentation says I should use the files->get() method on my Drive Service object with a parameter array containing "alt" => "media" to fetch the actual file content instead of just metadata.

Here’s what the docs show:

$documentId = '1AbcDefGhiJklMnOpQrStU2VwXyZ3456';
$response = $googleDriveService->files->get($documentId, array(
  'alt' => 'media'
));

What I don’t understand is what exactly gets stored in the $response variable. Does it contain the raw file data? If so, wouldn’t that cause memory issues with large files? Or maybe it returns some kind of stream that I can work with using fopen()? What’s the best way to write this data to a file on my server?

The official docs don’t explain what happens behind the scenes when you make this API call.

2

When you call files->get() with alt => media, you get a stream handle instead of the file loading straight into memory. I hit this same issue migrating from v2 last year. V3 gives you way more control over data transfer. For small files, just use $response->getBody()->getContents() to grab everything. For bigger files, work with the stream directly. I usually go with file_put_contents() since it handles memory management for you. Watch out though - some file types need extra OAuth permissions, especially Google Workspace docs that have to be exported instead of downloaded.

3

yep, the response object gives u a stream, which is awesome for memory! i often do fwrite(fopen('myfile.pdf', 'w'), $response->getBody()) and it works great. just remember to set your file permissions right or u might get weird errors when trying to write.

4

The $response variable isn’t raw binary data - it’s a Psr\Http\Message\ResponseInterface object. You need to call getBody() to get the actual file content. For small files, just use $response->getBody()->getContents() to grab it as a string, but that loads everything into memory at once. For bigger files, work with the stream directly. Use $response->getBody()->detach() to get the stream resource, then use standard PHP functions like stream_copy_to_stream() to write it locally without eating up all your memory. I’ve downloaded multi-GB files this way without any issues. The trick is knowing Google’s client returns PSR-7 response objects, so you control how the data stream gets handled.