how to make the newsletter checkbox checked by default in prestashop 1.7 in checkout process?

[prestashop.pp]

I will not write the question again since its written in stackoverflow:

https://stackoverflow.com/questions/44591989/how-to-make-the-newsletter-checkbox-checked-by-default-in-prestashop-1-7-in-chec

 

If someone knows how to do it in php it will be great.