[BUG][php] PHP api client is not working for file uploads

[jozefbriss]

There seems to be 2 issues:

1. The content is incorrect. Stringified PHP resource is included instead of the actual content of the file.
2. There is missing filename field in Content-Disposition header.

This is relevant part of the request by generated API. I have provided an instance of SplFileObject as an input for file field.

--boundary
Content-Disposition: form-data; name="file"

Resource id #202

The request should have been something like this looks like this.

--boundary
Content-Disposition: form-data; name="file"; filename="filename.txt"

[Actual content of the file not the stringified resource]

[jozefbriss]

This seems to be offending line:

openapi-generator/modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache

Line 115 in d7a7484

$result[$currentName] = ObjectSerializer::toString($val);

Changing this line:

                $result[$currentName] = ObjectSerializer::toString($val);

to this:

                $result[$currentName] = !is_resource($val) ? ObjectSerializer::toString($val) : $val;

fixes both problems.

[simonhammes]

I'm guessing this is similar to #21458 (php-nextgen) 🤷

@jozefbriss Can you create a PR for this?