Question 40132 in PHP Question posted in
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Download large file in PHP from Azure Blob Storage

I’m in the process of migrating a website offering large downloadable files (4GB and up) into Azure. I have successfully created the connection to the Azure storage account so I can retrieve the files. However the download a) takes ages to start and b) consumes loads of memory since I read the entire file into memory before actually sending the downloadable data to the client.
Is there a way to read the file in chunks from the Storage account to avoid the delay and memory consumption?
The current code looks like this:

$getBlobResult = $blobClient->getBlob($containerName,$FileName);
$blobProperties=($getBlobResult->getProperties());
$FileSize=$blobProperties->getContentLength();
// Send headers 
header ("Content-type: application/octet-stream");
header ("Content-Length: $FileSize");
header ("Content-Disposition: attachment; filename="$FileName"");
// Send content of file
echo stream_get_contents($getBlobResult->getContentStream());
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3

Answers


  1. 0

    For many reasons, I would recommend just serving the download directly from the storage. Mostly, because you have a big I/O performance impact and your traffic is also heavily loaded.

    Instead of using PHP I would suggest the following solutions – depending on what your hosting environment allows you to do.

    • Serve a URL of the file directly (using shared access signatures if a public URL is not an option)
    • If you don’t want to redirect the user to an azure link, download the file to your server with something like azcopy, rename it to some <hash>.<ext> and serve the direct URL to the user.
    • If you really need/want to use PHP, you can work through how to split a file and stream it to the user: How to upload data by chunks to Azure Blob Storage using PHP
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  2. 0

    Is there a way to read the file in chunks from the Storage account to
    avoid the delay and memory consumption?

    You can certainly do that. When downloading blob using getBlob method, you will need to specify the byte range you wish to download in the options parameter which is of type GetBlobOptions.

    If I am not mistaken, you would need to define the range in start-end format (e.g. 0-1023 to download 1KB)

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  3. 0

    Serving the file to the user via a signed URL as @CodeBrauer suggests would be the most preferable solution since you don’t have to pipe the data through your code/infrastructure at all.

    Though if that is at odds with your requirements, then you can try replacing:

    echo stream_get_contents($getBlobResult->getContentStream());

    With:

    fpassthru($getBlobResult->getContentStream());

    Which should just dump the stream straight out without needing virtually any buffer.

    https://www.php.net/manual/en/function.fpassthru

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