View with contextual filter by current user

hi,
I need to create a view with group members by Group module (not OG module) That show only members of group that current user belongs.
I Know That to create this view I need a custom PHP contextual filter but I’m not good in PHP.

how can I do it?

Thank you very much

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/4/feed