[Bug]: Undefined array key "output" in D:\XXX\vendor\openai-php\client\src\Responses\Responses\CreateResponse.php on line 116

Description

PHP Warning:  Undefined array key "output" in D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Responses\Responses\CreateResponse.php on line 116
PHP Fatal error:  Uncaught TypeError: OpenAI\Actions\Responses\OutputObjects::parse(): Argument #1 ($outputItems) must be of type array, null given, called in D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Responses\Responses\CreateResponse.php on line 116 and defined in D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Actions\Responses\OutputObjects.php:45
Stack trace:
#0 D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Responses\Responses\CreateResponse.php(116): OpenAI\Actions\Responses\OutputObjects::parse()
#1 D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Resources\Responses.php(45): OpenAI\Responses\Responses\CreateResponse::from()
#2 D:\PhpProjects\Farasat\Server\openai_test1.php(26): OpenAI\Resources\Responses->create()
#3 {main}
  thrown in D:\PhpProjects\Farasat\AppReq\proj_composer\vendor\openai-php\client\src\Actions\Responses\OutputObjects.php on line 45

Steps To Reproduce

my sample code is:

<?php
require_once(__DIR__ .'/../xxx/vendor/autoload.php');
$apiKey = 'sk-xxxxxxxxxxxxxxxxxxxxx';

$models=['gemini-2.0-flash','gpt-3.5-turbo','google/gemini-2.0-flash-exp:free','openai/gpt-4o-mini','gpt-4o'];
foreach($models as $model){
    try{
        $client = OpenAI::client($apiKey);
        echo '<br/>'.$model.'<br/>';
        $response = $client->responses()->create([
            'model' => $model,
            'input' => 'Hello!',
        ]);

        $result = json_decode($response, true);
        
        if($response!=null){
            echo ' response is NOT null';
            $var = print_r($response, true);
            echo $var;
            $var = print_r($result, true);
            echo $var;
            // echo $result['choices'][0]['message']['content'] ?? 'Error in response';
            break;
        }
        else{
            echo ' ------ response "'.$model.'" is null';
        }
    }
    catch (Exception $e) {
        echo $e->getMessage();
    }
}
?>

OpenAI PHP Client Version

v0.18.0

PHP Version

8.5.1

Notes

No response

Reproduce the sample request, then inspect CreateResponse.php at line 116 and OutputObjects.php at line 45 to compare the returned response shape with what the parser expects. Check each model in the example and verify that the affected response is handled without the undefined-key warning or TypeError.