Index Of Time .jpeg Can I Use PHP To Display A Random Background When My Website Loads?

Can I use PHP to display a random background when my website loads? - index of time .jpeg

Currently I have 7 background images as JPEG files. I would like to display a random image when the browser loads the page. Is it possible with PHP? Has anyone code? In addition, the index.html page requests that I will change it to index.php?