[lang php] allOf ignored

Description

GetSessionListResponse.yaml

description: Response for session list
allOf:
  - $ref: '../common/ApiResponse.yaml'
properties:
  response:
    $ref: '../../models/system/SessionList.yaml'

Variants without ref also don't works:

description: Response for session list
allOf:
  - type: object
    properties:
      success:
        type: boolean
      errors:
        type: array
        items:
          type: object
          properties: {}
      response:
        type: object
        properties: {}
  - type: object
    properties:
      response:
        type: object
        properties:
          memory:
            type: string

ApiResponse.yaml

type: object
properties:
  success:
    type: boolean
  errors:
    type: array
    items:
      type: object
      properties: {}
  response:
    type: object
    properties: {}

But generated with ignored properties success and errors from allOf: - $ref: '../common/ApiResponse.yaml':

GetSessionListResponse.md
# GetSessionListResponse

## Properties
Name | Type | Description | Notes
------------ | ------------- | ------------- | -------------
**response** | [**\Model\SessionList**](SessionList.md) |  | [optional]

[[Back to Model list]](../../README.md#documentation-for-models) [[Back to API list]](../../README.md#documentation-for-api-endpoints) [[Back to README]](../../README.md)

But if I use --lang openapi-yaml then all ok. Generated:

components:
  schemas:
    GetSessionListResponse:
      properties:
        response:
          $ref: '#/components/schemas/SessionList'
      description: Response for session list
      allOf:
      - $ref: '#/components/schemas/ApiResponse'

And correct documentation generated in https://editor.swagger.io/

Swagger-codegen version

swagger-codegen-cli-3.0.22.jar and swagger-codegen-cli-3.0.23.jar

Swagger declaration file content or url

openapi: 3.0.1
info:
  title:
  version:
servers:
- url:

paths:
  /system/getSessionList:
    get:
      responses:
        "200":
          description: successful operation
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/GetSessionListResponse'
components:
  schemas:
    GetSessionListResponse:
      description: Response for session list
      allOf:
      - $ref: '#/components/schemas/ApiResponse'
      - type: object
        properties:
          response:
            $ref: '#/components/schemas/SessionList'
    ApiResponse:
      type: object
      properties:
        success:
          type: boolean
        errors:
          type: array
          items:
            type: object
            properties: {}
        response:
          type: object
          properties: {}
    SessionList:
      type: object
      properties:
        sessions:
          type: object
          additionalProperties:
            $ref: '#/components/schemas/Session'
        memory:
          type: string
    Session:
      type: object
      properties:
        session:
          type: string

Command line used for generation

docker run --rm -v ${PWD}:/local -w /local openjdk java -jar swagger-codegen-cli.jar generate --input-spec /local/openapi.yaml --lang php --output /local/out/ -c /local/openapi-codegen-php.json

docker run --rm -v ${PWD}:/local -w /local openjdk java -jar swagger-codegen-cli.jar generate --input-spec /local/openapi.yaml --lang openapi-yaml --output /local/out/ -c /local/openapi-codegen-php.json

Steps to reproduce

Related issues/PRs

Suggest a fix/enhancement

Reproduce the issue with openapi.yaml and the swagger-codegen-cli 3.0.22 or 3.0.23 PHP command, then compare its output with the openapi-yaml generation. Start by locating the PHP generator's handling of the GetSessionListResponse allOf schema; done means the generated PHP documentation includes the inherited success and errors properties.