[PHP] Recursive builder pattern

TreeBuilder.php

<?php

/**
 * Recursive builder pattern
 *
 * Usage:

 * $tree = \Tree\Builder::init()
 *   ->setName('parent')
 *   ->addChild()
 *     ->setName('child 1')
 *     ->end()
 *   ->addChild()
 *     ->setName('child 2')
 *     ->addChild()
 *       ->setName('child 2.1')
 *       ->end()
 *     ->addChild()
 *       ->setName('child 2.2')
 *   ->build();
 *
 */

namespace Tree;

/**
 * @class Node
 */
class Node
{
  public $name;
  public $children;
  
  public function __construct()
  {
    $this->children = array();
  }
}

/**
 * @class Builder
 */
class Builder
{
  private $el;
  private $parent;
  
  /**
   * Private constructor
   */
  private function __construct(Node $el, Builder $parent = null)
  {
    $this->el = $el;
    $this->parent = $parent;
  }
  
  /**
   * Init the tree builder
   * @param $parent \Tree\Builder optional
   * @return \Tree\Builder
   */
  static function init(Builder $parent = null)
  {
    return new self(new Node(), $parent);
  }
  
  /**
   * Set node name
   * @param $name string
   * @return \Tree\Builder
   */
  function setName($name)
  {
    $this->el->name = $name;
    return $this;
  }
  
  /**
   * Add a child node
   * @return \Tree\Builder child builder
   */
  function addChild()
  {
    $builder = self::init($this);
    $this->el->children[] = $builder->el;
    return $builder;
  }
  
  /**
   * Return to the parent builder (or itself if root)
   * @return \Tree\Builder
   */
  function end()
  {
    if ($this->parent == null)
    {
      return $this;
    }
    else
    {
      return $this->parent;
    }
  }
  
  /**
   * Return the final object
   * @return \Tree\Node
   */
  function build()
  {
    if ($this->parent == null)
    {
      return $this->el;
    }
    else
    {
      return $this->parent->build();
    }
  }
}