<?php
class ArrayStack
{
  private $size;
  private $stack = [];
  public function __construct(){}
  public function buildStack($num){
    $this->size = $num;
    $index = 0;
    while($index ++ < $this->size)
    {
      $this->stack[] = $index;
    }
  }
  public function pop(){
    $item = array_shift($this->stack);
    $this->size = count($this->stack);
    return $item;
  }
  public function push($item)
  {
    $this->stack[] = $item;
    $this->size = count($this->stack);
  }
  public function size()
  {
    return $this->size;
  }
  public function stack()
  {
    return $this->stack;
  }
}
interface Joseph
{
  public function handle($num = 0, $step = 0, $survivors = 0);
}
class StackJoseph implements Joseph
{
  protected $stack;
  protected $num;
  protected $step;
  public function __construct(ArrayStack $stack)
  {
    $this->stack = $stack;
  }
  public function handle($num = 0, $step = 0, $survivors = 0)
  {
    // TODO: Implement handle() method.
    $this->stack->buildStack($num);
    $i = 0;
    while($this->stack->size() > $survivors)
    {
      $pop = $this->stack->pop();
      if(($i + 1) % $step !== 0)
      {
        $this->stack->push($pop);
        $i ++;
      }
      else
      {
        $i = 0;
      }
    }
    return $this->stack->stack();
  }
}
function joseph($num, $step, $survivorsNum)
{
  $arrayStack = new ArrayStack();
  $joseph = new StackJoseph($arrayStack);
  return $joseph->handle($num, $step, $survivorsNum);
}
print_r(joseph(41, 3, 2));

Array
(
  [0] => 16
  [1] => 31
)