How can the use of global variables like $GLOBALS in PHP lead to issues and what are alternative methods for managing variables across files?

Using global variables like $GLOBALS in PHP can lead to issues such as making code harder to debug, maintain, and test. It can also introduce unexpected side effects and make it difficult to track where variables are being modified. One alternative method for managing variables across files is to use classes and objects to encapsulate data and functionality. This helps in organizing code, reducing dependencies, and improving code reusability. Another method is to use functions to pass variables as parameters rather than relying on global scope.

// Using classes and objects to manage variables across files
class DataManager {
    private $data;

    public function __construct($data) {
        $this->data = $data;
    }

    public function getData() {
        return $this->data;
    }

    public function setData($data) {
        $this->data = $data;
    }
}

// Usage example
$dataManager = new DataManager("Hello, World!");
echo $dataManager->getData();
$dataManager->setData("Goodbye, World!");
echo $dataManager->getData();