Problem:
Loop through the repeatable field groups using PHP code

Solution:
To query the repeating field group posts using PHP - you can use the post relationship API function toolset_get_related_posts .

You can find proposed solution, in this case, with the following reply:
https://toolset.com/forums/topic/loop-through-the-repeatable-field-groups-using-php-code/#post-948459

Relevant Documentation:
https://toolset.com/documentation/customizing-sites-using-php/post-relationships-api/#toolset_get_related_posts