What is encapsulation in Object Oriented Programming (OOP)?

Wrapping up data member and method together into a single unit (i.e. Class) is called Encapsulation.
Encapsulation is like enclosing in a capsule. That is enclosing the related operations and data related to an object into that object.
Encapsulation is like your bag in which you can keep your pen, book etc. It means this is the property of encapsulating members and functions.

view source code

Encapsulation means hiding the internal details of an object, i.e. how an object does something.
Encapsulation prevents clients from seeing its inside view, where the behaviour of the abstraction is implemented.
Encapsulation is a technique used to protect the information in an object from the other object.

Hide the data for security such as making the variables as private, and expose the property to access the private data which would be public.
So, when you access the property you can validate the data and set it.

Example:
<?php
class YourMarks
{
private $mark;
public Marks
{
get { return $mark; }
set { if ($mark > 0) $mark = 10; else $mark = 0; }
}
}
?>

Below the real life example of encapsulation:

1. I am giving example of Mobile Phone and it’s Manufacture:

Let’s take example of Mobile Phone and Mobile Phone Manufacturer
Suppose you are a Mobile Phone Manufacturer and you designed and developed a Mobile Phone design(class), now by using machinery you are manufacturing a Mobile Phone(object) for selling, when you sell your Mobile Phone the user only learn how to use the Mobile Phone but not that how this Mobile Phone works.

This means that you are creating the class with function and by making object (capsule) of it you are making availability of the functionality of you class by that object and without the interference in the original class.

2. I am giving an another example of real life (daily use) that is “TV operation”. Many peoples operate TV in daily life.

It is encapsulated with cover and we can operate with remote and no need to open TV and change the channel.
Here everything is in private except remote so that anyone can access not to operate and change the things in TV.

Encapsulation binds together the data and functions that manipulate the data, keeping it safe from interference and misuse.

Real World Example: Every time you log into your email account( GMail, Yahoo, Hotmail or official mail), you have a whole lot of processes taking place in the backend, that you have no control over. So your password, would probably be retrieved in an encyrpted form, verified and only then you are given access. You do not have any control, over how the password is verified, and this keeps it safe from misuse.

Abstraction is a process of hiding the implementation from the user, only the functionality is exposed here. So you are aware only of what the application does, not how it does it.

Real World Example: When you log into your email, compose and send a mail. Again there is a whole lot of background processing involved, verifying the recipient, sending request to the email server, sending your email. Here you are only interested in composing and clicking on the send button. What really happens when you click on the send button, is hidden from you.