Are PHP files usable by others when I put my website online?

I created a website using html and css files which I know are supported by web browsers. I also created a php page which is linked to index.html. If I put these files online and make it publicly accessible will my php file work for other users the way it works for me on my localhost? Also, I am using MAMP PRO's free demo so will I need to buy an apache server to ensure that the php file still works for others?