identifying OOP fundamental parts - SportsRecruits/OOP-workshop

FirstDay.php

<?php

/*
Research about:
- OOP PHP INHERITANCE
- OOP PHP INTERFACES
- Polymorphism 
*/


//
//extends, implements (contract, protocol, ENFORCEMENT (ARMY))

interface AccountContract
{
    public function setPost();
    public function getPost();
}

class Account implements AccountContract //<--- is this correct?
{
    public function setPost($post)
    {

    }
    public function getPost()
    {

    }
}

class InstagramAccount implements AccountContract //<----- how about this?
{
    public function setPost($post)
    {
        // INstagramAPI::post();
    }
    public function getPost()
    {
        //
    }
}

class FacebookAccount
{
    public function setPost($post)
    {
        // FacebookAPI::post();
    }
    public function getPost()
    {
        //
    }
}

//Class used to identify all the main parts involved in OOP. 
class Account
{
    protected $amount = 0;
    // private $a = 'i am a';
    // public $b = 'foo';

    public function __construct($amount)
    {
        $this->setDeposit($amount);
    }

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

    public function getAmount()
    {
        return $this->convertToJapanCurrency($this->amount);
    }

    protected function convertToJapanCurrency($a)
    {
        return 'SERGARTERAW' . $a;
    }
}

class User
{
    public function deposit()
    {
        // (new Account)->b; //work
        // (new Account)->a; //wont work
        // (new Account)->amount; //= 100;
        $account = (new Account(100));
        $account->setDeposit(100);
        $account->getAmount(); //200
    }

}