What best practices should be followed when streaming or downloading large files in PHP to ensure efficient memory usage and uninterrupted transfers for users with varying internet speeds?

When streaming or downloading large files in PHP, it's important to use output buffering and chunked transfer encoding to efficiently handle memory usage and ensure uninterrupted transfers for users with varying internet speeds. By sending the file in smaller chunks, you can reduce memory consumption and allow the user to start downloading the file before it's fully loaded.

// Set appropriate headers for streaming and chunked transfer encoding
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="large_file.zip"');
header('Transfer-Encoding: chunked');

// Open the file for reading
$handle = fopen('path/to/large_file.zip', 'rb');

// Stream the file in chunks
while (!feof($handle)) {
    echo fread($handle, 8192); // Adjust chunk size as needed
    ob_flush();
    flush();
}

// Close the file handle
fclose($handle);