Encapsulation

Benefit:

1. Variable & Method can be well protected. 
2. Increase the code reusability.

Example:


The name can only modified by the constructor
$student = new Student('John Doe');

The age can only modified by setAge method
$student->setAge(14);

The $age cannot be direct accessed
$student = new Student('John Doe');
$student->age = 14;