<?php

error_reporting(-1);
mb_internal_encoding('utf-8');

class Worker {
  public $name;
  public $level;
  public $chief; // Принимает значения True or False


  function __construct($workers_name, $workers_level, $is_chief) {
    $this->name = $workers_name;
    $this->level = $workers_level;
    $this->chief = $is_chief;
  }
}
class Manager extends Worker {

  protected $paid = 500;
  protected $pages = 200;
  protected $coffe = 20;

  public function drinkCoffe() {
    if ($this->chief == True) {
      return ($this->coffe * 2);
    } else {
      return $this->coffe;
    }
  }
}
$Peter = new Manager('P. Stivenson', 2, True);
echo $Peter->drinkCoffe();

/* Стоит создать для каждого типа работника - отдельный подкласс Worker */
?>