[BUG][PHP] Array is not taken into account when content is multipart/form-data

Created by: atanasiuk-hubspot

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• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
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Description

Array is not taken into account when content is multipart/form-data (PHP client). Exception is thrown:

Fatal error: Uncaught RuntimeException: Unable to open Array using mode rb: fopen() expects parameter 1 to be a valid path, array given

openapi-generator version

4.3.1

OpenAPI declaration file content or url

"requestBody" : {
  "content" : {
    "multipart/form-data" : {
      "schema" : {
        "properties" : {
          "files": {
            "type": "array",
            "items": {
              "type": "string",
              "format": "binary"
            },
            "description": "A list of files containing the data to import"
          }
        }
      }
    }
  }
}

Command line used for generation

Generating php client with

java -jar openapi-generator-cli-4.3.1.jar -g php

Steps to reproduce

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