php-nextgen - Fix flatten() to support arrays of files

[lukascernydis]

Previously, FormDataProcessor::flatten() unconditionally passed all values through ObjectSerializer::toString(), which caused an error when flattening arrays containing file resources (e.g. for OpenAPI multipart/form-data definitions with type: string, format: binary).

This change adds a check for is_resource() to preserve stream handles without serialization, ensuring correct behavior when uploading files.

The error is not in generator itself but rather in the generated utility PHP class FormDataProcessor.php

Reproducible by generating method that utilizes any file or file list. For example:

            requestBody:
                required: true
                content:
                    multipart/form-data:
                        schema:
                            type: object
                            required:
                                - files
                            properties:
                                files:
                                    type: array
                                    items:
                                        type: string
                                        format: binary

@renepardon

[wing328]

thanks for the pr

please follow step 3 to update the samples

[wing328]

thanks again for the fix

is it correct to say that you've been using this fix and confirm it's working as expected ?

[lukascernydis]

Yes, after this edit, the TypeError no longer appears in ObjectSerializer::toString($val) and file is correctly included in the request. Same for list of files.

Thank you for guiding me.

[wing328]

thanks for the PR

let's give it a try