Comb.php

<?php
/*
 * Mask before start
 * 000000
 * 111111
 * 222222
 *
 * First row
 * 001122
 *
 * Mask after first row
 * 110000
 * 222211
 *
 * Two rows
 * 001122
 * 120201
 *
 * Mask after second row
 * 212010
 */
class Comb {

  protected $elements_count;

  protected $row_count;

  protected $columns_count;

  protected $mask;

  public function call(int $elements_count) {
    $this->elements_count = $elements_count;
    $this->row_count = $elements_count;
    $this->mask();
    $result = [];
    $x = 0;
    $y = 0;
    for ($row_index = 0; $row_index < $this->row_count; $row_index++) {
      $repeat_count = $this->fact($this->row_count - $row_index - 1);
      $mask_row = 0;
      for ($group_index = 0; $group_index < ($this->columns_count / $repeat_count); $group_index++) {
        if ($mask_row >= count($this->mask[$x])) {
          $mask_row = $mask_row % count($this->mask[$x]);
        }
        $repeat_value = $this->mask[$x][$mask_row];
        for ($repeat_index = 0; $repeat_index < $repeat_count; $repeat_index++) {
          $result[$x][$y] = $repeat_value;
          unset($this->mask[$x][$mask_row]);
          $this->mask[$x] = array_values($this->mask[$x]);
          $x++;
          if ($x == $this->columns_count) {
            $x = 0;
          }
        }
        $mask_row++;
      }
      $y++;
    }

    return $result;
  }

  protected function mask() {
    $this->columns_count = $this->fact($this->elements_count);
    $mask = [];
    for ($column_index = 0; $column_index < $this->columns_count; $column_index++) {
      for ($row_index = 0; $row_index < $this->row_count; $row_index++) {
        $mask[$column_index][$row_index] = $row_index;
      }
    }

    $this->mask = $mask;
  }

  protected function fact(int $number) {
    $factorial = 1;
    for ($i = 1; $i <= $number; $i++){
      $factorial = $factorial * $i;
    }
    return $factorial;
  }

}

$c = new Comb();
$r = $c->call(4);

foreach ($r as $row){
  foreach ($row as $value) {
    echo $value . '  ';
  }
  echo "\n";
}