Cannot seem to view the index.php in firefox

I am quite new to the Localhost view and have done quite alot in the building database driven website 4th edition, I have installed all the PHP Apache and sql seperately and they have worked on lots of testing and learning…
But now I have started another tutorial and I have created a new folder in my HTDocs in Apache and saved a file index.php and go to look at it in the Localhost/foldername and it just lists the directory of the htdocs instead of the index.php, when I search through myComputer/programs files/ apache/./. to the folder and look in it, there is no index.php showing, but when i save as and select the correct path to the folder in apache it says it already exists, do I want to replace it. I don’t understand? why I cant see it…When I did the tutorials from the book the files were named .html.php does this make any difference.
I am running win7.
Thank You for any help…

What if you put index.html in the same folder as index.php? Can you see that?