PHP OOP · Episode 10

OOP: Encapsulation (public / private / protected)

Hide your data — and control how it changes

ep10_oop_encapsulation.php

<?php

class BanksAccount {

  private $balance;

  public function makeDeposit($amount){

    if($amount > 0){
      $this->balance = $this->balance+$amount;
    }
    else{
      throw new error("Negative deposit is not possible");
    }
    
  }

  public function showBalance(){
    return "Your account balance is $this->balance INR";
  }

}

$bank = new BanksAccount();
$bank->makeDeposit(100);
// -50 is avoided
//$bank->makeDeposit(-50);
$bank->makeDeposit(50);

Output

Output for this tutorial goes here.

Your account balance is 150 INR

The Problem

If a property is public, anyone can change it from anywhere — even to something invalid, like a negative bank balance. Nothing stops it, and bugs sneak in.

Encapsulation

Encapsulation means hiding an object’s data and only letting the outside world touch it through methods you control. The data stays safe; the rules live in one place.

The three access modifiers

public — reachable from anywhere.

private — only from inside the same class.

protected — from the class and its child classes (matters once we hit inheritance).

Getters & Setters

Make the data private, then expose a method to read it (showBalance()) and an action to change it (makeDeposit()) — where you can validate first. Here a deposit must be greater than 0, otherwise it’s rejected.

Example Output

makeDeposit(100) then makeDeposit(50) → Your account balance is 150 INR

$bank->balance = 999999; → Error: cannot access private property

Key takeaway: make data private and control access through methods. It keeps your object’s state valid and lets you change the internals later without breaking the code that uses it.

Pro tips: use protected when child classes need access. In PHP 8.1+, readonly properties can be set once (in the constructor) and never changed — encapsulation without a setter.

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