What are the potential drawbacks of extending a class like "Registry" with another class like "Config" in PHP?

Extending a class like "Registry" with another class like "Config" can lead to a tight coupling between the two classes, making the code harder to maintain and understand. Instead of extending the "Registry" class with "Config", it is better to create a separate class that encapsulates the configuration logic and use it within the "Registry" class as needed. 

class Registry {
    private $data = [];

    public function set($key, $value) {
        $this->data[$key] = $value;
    }

    public function get($key) {
        return $this->data[$key];
    }
}

class Config {
    private $configData = [];

    public function setConfig($key, $value) {
        $this->configData[$key] = $value;
    }

    public function getConfig($key) {
        return $this->configData[$key];
    }
}

// Usage
$registry = new Registry();
$config = new Config();

$config->setConfig('db_host', 'localhost');
$config->setConfig('db_user', 'root');

$registry->set('config', $config);

echo $registry->get('config')->getConfig('db_host'); // Output: localhost

Keywords

Registry Config class extension inheritance PHP

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