[BUG][php] json_decode missing when response is object

Created by: ybelenko

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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When I call API via generated PHP client I got encoded json string instead of decoded object. Response looks like:

["{\"foobar\":\"foobaz\"}"]

openapi-generator version

5.0.0-beta

OpenAPI declaration file content or url

paths: 
  '/objects/{id}':
    parameters:
      - name: id
        in: path
        required: true
    get:
      operationId: getSingleObjectById
      responses:
        '200':
          description: ok
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FreeFormObject'
components:
  schemas:
    FreeFormObject:
      type: object

Generation Details

generate -i \"spec.yaml\" -g php -o \"api-client-sdk\"

Steps to reproduce

Send request via generated SDK to staged server /objects/1 where response is correct JSON item. The response will be json encoded string instead of object.

Related issues/PRs

#6566 Seems close but not really. I'm ok with response as object instead of model. It's just json_decode execution missed.

Suggest a fix

diff --git a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
index 58200ac713..42fd2658d1 100644
--- a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
@@ -294,6 +294,7 @@ class ObjectSerializer
         }
 
         if ($class === 'object') {
+            $data = is_string($data) ? json_decode($data) : $data;
             settype($data, 'array');
             return $data;
         }

I don't know why json_decode executes based on string check and doesn't check Content-Type header but it's a quick fix.