yiisoft/yii2 · error · InvalidConfigException

Object configuration must be an array containing a "class" o

Error message

Object configuration must be an array containing a "class" or "__class" element.

What it means

When Yii::createObject() receives an array it requires a class reference: '__class' or 'class'; every remaining key becomes container/config input. An array with neither key cannot name a class to instantiate, so InvalidConfigException is thrown. Note that '__class' takes precedence and also strips a legacy 'class' key when both are present, and the isset check is case-sensitive ('Class'/'__Class' do not count).

Source

Thrown at framework/BaseYii.php:374

        }

        if (!is_array($type)) {
            throw new InvalidConfigException('Unsupported configuration type: ' . gettype($type));
        }

        if (isset($type['__class'])) {
            $class = $type['__class'];
            unset($type['__class'], $type['class']);
            return static::$container->get($class, $params, $type);
        }

        if (isset($type['class'])) {
            $class = $type['class'];
            unset($type['class']);
            return static::$container->get($class, $params, $type);
        }

        throw new InvalidConfigException('Object configuration must be an array containing a "class" or "__class" element.');
    }

    private static $_logger;

    /**
     * @return Logger message logger
     */
    public static function getLogger()
    {
        if (self::$_logger !== null) {
            return self::$_logger;
        }

        return self::$_logger = static::createObject('yii\log\Logger');
    }

    /**
     * Sets the logger object.

View on GitHub (pinned to 66f00d18a2)

Solutions

1. Add 'class' => Your\Class::class as the first key of the array
2. If the array comes from merging, check merge order and structure - the base array must carry the 'class' key
3. Dump the array right before the createObject call to see where the key is lost, then fix the producer

Example fix

// before
$mutex = Yii::createObject(['expire' => 30]);

// after
$mutex = Yii::createObject([
    'class' => \yii\mutex\FileMutex::class,
    'expire' => 30,
]);

if (is_array($config) && !isset($config['class']) && !isset($config['__class'])) {
    throw new \InvalidArgumentException('Config array needs a class or __class key');
}
$object = Yii::createObject($config);

try {
    $object = Yii::createObject($config);
} catch (\yii\base\InvalidConfigException $e) {
    // message: Object configuration must be an array containing a "class" or "__class" element.
    Yii::error('Missing class key in config: ' . print_r($config, true));
    throw $e;
}

When it happens

Trigger: Yii::createObject(['ttl' => 3600]) - pure options with no class key; config assembled with ArrayHelper::merge where a later array overwrote or dropped the map carrying 'class'; keys typo'd as 'Class' or '_class'; arrays decoded from JSON where the class key was removed.

Common situations: Overriding a vendor extension's config and replacing instead of merging; dynamically assembled configuration from multiple sources; partial copy-paste of an example snippet whose class line was not copied.

Related errors

• Unsupported configuration type: ' . gettype($type)
• Invalid path alias: $alias
• The "id" configuration for the Application is required.
• The "basePath" configuration for the Application is required
• Unknown bootstrapping component ID: $mixed

AI-assisted analysis of yiisoft/yii2@66f00d18a2 (2026-08-17). Data as JSON: /api/errors/d8fed80bfc03ada5. Report an issue: GitHub.