Show product commerce by taxonomy parent with childs
Well, I am my most popular fan so I will answer myself:
1. It's not possible to add that PHP code to the view, as it's a known bug that the view doesn't allow multiple contextual filter variables as a PHP. Although you can use them through the URL and changing the 'code PHP' option by 'Multiple Terms ID separated by ',' OR '+''. --&gt; I don't like that option as the URL won't be very clean and can be a bit complicated.
2. Found a better option!! I decided to select the parent when one of its childs are selected. This option can be activated as automatically, when installing the Taxonomy Term Reference Tree Widget module:

About this module
This module provides an expandable tree widget for the Taxonomy Term Reference field in Drupal 7. This widget is intended to serve as a replacement for Drupal's core Taxonomy Term Reference widget, which is a flat list of radio buttons or checkboxes and not necessarily fit for medium to large taxonomy trees.

Note: I don't know why but my tree view is not as nice as in the picture and I needed to use a fix but it works perfect.