cURL - Send 2+ files using the same parameter name ("file[]")

Description

The pull request https://github.com/php/php-src/pull/8292 made it possible to send an array of parameters of the same name.

However, it doesn't seem to support files:

I'm using PHP 8.3, but I'm not succeeding in doing this:

curl_setopt($ch, CURLOPT_HTTPHEADER, [
	'Content-Type: multipart/form-data'
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
	'file' => [
		new CURLFile($file1, posted_filename: 'File1.jpg'),
		new CURLFile($file2, posted_filename: 'File2.jpg')
	]
]);

PHP Fatal error: Uncaught Error: Object of class CURLFile could not be converted to string

Would it be possible to fix this, please?

Thank you very much!

Start by tracing the PHP cURL handling for CURLOPT_POSTFIELDS, CURLFile values, and multipart/form-data arrays, using the reproduction in the issue and the earlier array-parameter change in pull request 8292 as entry points. Verify the behavior with two CURLFile objects under one field name; done means both files are encoded and sent without the object-conversion fatal error, with regression coverage added.