//User.php
<?php

abstract class User
{
    protected $userName;
    protected $password;
    protected $wrongLoginCounter = 0;
    protected $age;

    abstract public function checkLogin($username, $password);

    public function setLogin($userName)
    {
        $this->userName = $userName;
    }

    abstract public function setPassword($password);

    abstract public function setAge($age);

    final public function login($username, $password)
    {
        if ($this->wrongLoginCounter >= 3) {
            return false;
        }

        return $this->checkLogin($username, $password);
    }
}
////Admin.php
<?php
require __DIR__ . '/User.php';

class Admin extends User
{
    public function setAge($age)
    {
        $this->age = $age;
    }

    public function checkLogin($username, $password)
    {
        if (!$username || $username != $this->userName || $this->password != $password) {
            $this->wrongLoginCounter++;
            return false;
        }
        $addressParts = explode('.', $_SERVER['REMOTE_ADDR']);

        $validAddress = [127, 192];

        if (!in_array($addressParts[0], $validAddress)) {
            $this->wrongLoginCounter++;
            return false;
        }

        return true;
    }

    public function setPassword($password)
    {
        if (strlen($password) < 10 || !is_int($this->age) || $this->age <= 0) {
            return false;
        }

        $this->password = $password;
    }
}

$admin = new Admin();
$admin->setLogin('Paweł');
$admin->setAge(23);
$admin->setPassword('tajneHasłoPaweła');

echo '<pre>';
var_dump($admin->login('Paweł', 'asd'));
echo '</pre>';
die;;


//Client.php
<?php
require __DIR__ . '/User.php';

class Client extends User
{
    public function setAge($age)
    {
        $this->age = $age;
    }

    public function checkLogin($username, $password)
    {
        if (!$username || $username != $this->userName || $this->password != $password) {
            $this->wrongLoginCounter++;
            return false;
        }

        $this->wrongLoginCounter = 0;

        return true;
    }

    public function setPassword($password)
    {
        if (strlen($password) < 8 || !is_int($this->age) || $this->age <= 17) {
            return false;
        }

        $this->password = $password;
    }
}

$client = new Client();
$client->setLogin('Paweł');
$client->setAge(23);
$client->setPassword('tajneHasłoPaweła');

echo '<pre>';
var_dump($client->login('Paweł', 'asd'));
echo '</pre>';
die;;