OOP — কনস্ট্রাক্টর, ইনহেরিটেন্স, আর ভিজিবিলিটি

<?php
  class Student {
    public $name;
    public $course;

    public function __construct($name, $course) {
      $this->name = $name;
      $this->course = $course;
    }
  }

  $student = new Student("Priya", "Web Development"); // set in one line
?>

<?php
  class BankAccount {
    private $balance = 0;

    public function deposit($amount) {
      $this->balance += $amount;
    }

    public function getBalance() {
      return $this->balance;
    }
  }

  $account = new BankAccount();
  $account->deposit(500);
  echo $account->getBalance(); // 500
  // echo $account->balance; // Error — private, not accessible from outside
?>

<?php
  class Person {
    public $name;

    public function __construct($name) {
      $this->name = $name;
    }

    public function greet() {
      return "Hi, I'm {$this->name}.";
    }
  }

  class Student extends Person {
    public $course;

    public function __construct($name, $course) {
      parent::__construct($name); // reuse Person's constructor
      $this->course = $course;
    }
  }

  $s = new Student("Amit", "Graphic Design");
  echo $s->greet(); // "Hi, I'm Amit." — inherited from Person, unchanged
?>