If you want 'index.php' to take priority then the answer is Yes.
When it comes doubt about using a particular file and/or replacing with another you are not will work properly, then rename the file on your Hosting account. This allows one to test the new changes/file and if things go wrong, you can rename the file back to what it was.
In this case, rename 'index.html' to 'index.html1' and it won't work anymore but easy to change back if you want to work again.




