[BUG] [PHP] array of objects class triggers Fatal Error

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

Php generator makes fatal error for array of object
class ListOfMessage has no parent but it has this method with 'parent' call

class ListOfMessage implements ModelInterface, ArrayAccess, \JsonSerializable
{
    public function listInvalidProperties()
    {
        $invalidProperties = parent::listInvalidProperties();

        return $invalidProperties;
    }
}

And fatal error happens
Deprecated: Cannot use "parent" when current class scope has no parent in
I have no acces to api and can't change it to

              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Message'

Also ObjectSerializer::deserialize doesn't unserialize such object properly: it empty

openapi-generator version

5.1 and latest from dockerhub

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  description: Chat API
  version: "1.0.0-oas3"
  title: Chat API
  contact:
    email: spatialguru.net@gmail.com
  license:
    name: Apache 2.0
    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
tags:
  - name: admins
    description: Secured Admin-only calls
  - name: developers
    description: Operations available to regular developers
paths:
  '/api/v1/chat/{acctNum}/room/{id}/messages':
    get:
      tags:
        - developers
      summary: searches for messages by room
      operationId: messagesByRoomV1
      parameters:
        - in: path
          name: acctNum
          description: Account number of organization
          required: true
          schema:
            type: string
        - in: path
          name: id
          description: Chat room id
          required: true
          schema:
            type: integer
      responses:
        '200':
          description: search results matching criteria
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ListOfMessage'
        '400':
          description: bad input parameter
        '403':
          description: >-
            forbidden if account number does not match user organization account
            number and user is not a super-admin
        '500':
          description: internal server error
servers:
  - url: 'https://test.fake.io'
components:
  schemas:
    ListOfMessage:
      type: array
      items:
        $ref: '#/components/schemas/Message'
    Message:
      required:
        - id
        - createdOn
        - updatedOn
        - owner
        - ownerName
        - content
        - chatRoomId
      properties:
        id:
          type: integer
        createdOn:
          type: integer
        updatedOn:
          type: integer
        owner:
          type: integer
        ownerName:
          type: string
        content:
          type: string
        chatRoomId:
          type: integer`

Start by running the Makefile .generate target with the provided OpenAPI schema. Inspect the generated ListOfMessage class and ObjectSerializer::deserialize behavior for array-of-object models. Done means generation no longer emits a parent call for a class without a parent and deserialization produces the expected objects.