Encapsulation :

Encapsulation is the mechanism that binds together code and the data it manipulates, and keeps both safe from outside interference and misuse. The wrapping up of data and methods into a single unit (called class) is known as encapsulation. The benefit of encapsulating is that it performs the task inside without making you worry.

example:
    <?php
    class App {
	    private static $_user;
	    public function User( ) {
		    if( $this->_user == null ) {
			    $this->_user = new User();
		    }
		    return $this->_user;
	    }
    }
    class User {
	    private $_name;
	    public function __construct() {
		    $this->_name = "S Mohan Kumar";
	    }
	    public function GetName() {
		    return $this->_name;
	    }
    }
    $app = new App();
    echo $app->User()->GetName();
    ?>
After editing Click here:
Output:
Hello World