Is it considered a best practice to use global variables like $_SESSION for storing data in PHP applications, or are there better alternatives?

Using global variables like $_SESSION for storing data in PHP applications is considered a common practice. However, it is important to be cautious when using global variables as they can lead to potential security vulnerabilities and make code harder to maintain. It is recommended to use more structured approaches like dependency injection or a dedicated data storage solution like a database or caching system.

// Example of using dependency injection to store and retrieve data
class DataStorage {
    private $data = [];

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

    public function retrieveData($key) {
        return isset($this->data[$key]) ? $this->data[$key] : null;
    }
}

// Implementation
$dataStorage = new DataStorage();
$dataStorage->storeData('user_id', 123);

$user_id = $dataStorage->retrieveData('user_id');
echo $user_id; // Output: 123