Slowing Down Dynamic Changes

So the issue I have is there is a rotating carousel in one of the pages of the site. It will show a picture and text in a layout like a banner and then switch to the other one a few seconds later. The client says it goes by too fast. I found the code for the display in on of the PHP files in the editor. I found out it uses an infinite PHP loop to rotate among the displays. I tried initially to use the PHP sleep function in the loop to try to delay the iterations of the loop, but it didn’t affect the iteration time. So now, I am a little puzzled. Is there another way to do this? I even tried the setTimeout javascript function in the lop and that didn’t work either. Thank you for any help.