$this and Self

<?php

// Dúvida referente ao post http://forum.tableless.com.br/t/ajuda-com-o-this-e-self/1095

//$u = new User();
//$u->find();

echo "<pre>";
var_dump(User::forge()->find());

class BaseModel
{
  private $_table = null;

  public function __construct($table)
  {
    $this->_table = $table;
  }

  public function find(array $params = [])
  {
    die($this->table);
  }
}

class User extends BaseModel
{
  protected $table = "users";

  public function __construct()
  {
    $this->_table = $this->table;
  }

  public static function forge()
  {
    return new self;
  }

  public function find(array $params = [])
  {
    parent::find($params);
  }
}