That has to be done with JQuery. One of the ‘P”s in PHP is "preprocessor", which means that this language is run before the file is sent out to the browser. In short, it is impossible to manipulate anything on the page with PHP once it is loaded into the browser. PHP could access a database, pull out all the images you want, and send them out. You then need Javascript to manipulate them like that client-side.
If you’d like to learn more about PHP, I suggest hitting up some online resources to learn how it all works. Or, you could hit up a library.
Best of luck, and please shoot me a message if you have any questions.
-D
