Get Month First Date of last six months

I wish to fetch all the first day dates starting from last six months. How to do this in laravel?

I know that I can do this as like this :-

$firstDay = new \Carbon\Carbon('first day of January 2018'); $firstDay = new \Carbon\Carbon('first day of Febuary 2018'); $firstDay = new \Carbon\Carbon('first day of March 2018'); $firstDay = new \Carbon\Carbon('first day of April 2018');

and so on.. but I need to write in everytime for each month. I want to make it dynamic so that for every new month I can get the date.