How can the use of setters and getters in PHP classes impact data validation and security measures?

Using setters and getters in PHP classes can impact data validation and security measures by allowing you to control access to class properties and validate the data being set. By implementing setters, you can enforce specific validation rules before allowing data to be stored in class properties, thus increasing the security of your application. Getters can also be used to retrieve data in a controlled manner, preventing unauthorized access to sensitive information.

class User {
    private $username;

    public function setUsername($username) {
        // Validate username before setting
        if (strlen($username) >= 5) {
            $this->username = $username;
        } else {
            throw new Exception("Username must be at least 5 characters long");
        }
    }

    public function getUsername() {
        return $this->username;
    }
}

$user = new User();
$user->setUsername("john_doe");
echo $user->getUsername(); // Output: john_doe