Access Modifiers

PHP 5 gives us everything we would expect in this area. In previous versions of PHP there was no support for data protection, meaning that all elements of a class were publicly accessible. This lack of access modifiers was probably the biggest disincentive to using objects in PHP 4.

A notion closely related to data protection is information hiding. Access modifiers make information hiding possible by exposing an interface. This is also referred to as encapsulation of an object.