What are the reasons for using private or protected visibility in PHP classes?

Using private or protected visibility in PHP classes helps to encapsulate the internal workings of a class and prevent direct access to its properties and methods from outside the class. This helps to maintain the integrity of the class and reduces the risk of unintended modifications or dependencies on its internal implementation details.

class Example {
    private $privateProperty;
    protected $protectedProperty;
    
    private function privateMethod() {
        // private method implementation
    }
    
    protected function protectedMethod() {
        // protected method implementation
    }
}