To be honest, you don't need any php at all. People upthread already mentioned using ajax to get the next/previous quotes; why not go a step further and send it all to the user in a straight js file?

Think about it: you said you scraped the data, so it's not like it's going to be constantly updated - when it changes, it will all change at once and you can update the versions of your data files. And there's only a fairly small amount of data, especially compared to the size of your css and background images (1000 short quotes with title/author/image/url will be well under 500kB, and the compression ratio will be much better than images).

(hmm, 500kB might actually be too big - perhaps have 10 separate .js files with 100 quotes each, and download a new block when needed? If you shuffle the order of the blocks and then within each block, it will appear "random enough" to users)

So, far less server load, and much faster for the user too. Makes the forward/back problem someone mentioned much easier to solve too - the browser can remember everything itself, and you don't need to track anything server-side.