openin home page as index.php

i am trying to find the solution of this problem for weeks ??
the prolem is that when somebody enters a adress https://www.sitename.com i want this url to be https://www.sitename.com/index.php

for the solution i create a index.html and forward it to index.php.but i didn’t like this solution(it was openin too late)

i want to use .htaccess but then i learnt that my server is windows.so i foundd another solution to solve this and i use php.ini file to solve this problem.but when i thought that the problem is gone in firefox the page was opening like what i want but in internet explorer it opens like https://www.sitename.com.

so please help me and save me from this situation ??