The http response headers should have cache-control settings. The headers are visible if you do curl -v <url>. The app platform will use default settings if it isn’t found. The defaults are to prevent caching on services (as they usually have dynamic content), and static sites default to allowing caching for a while (like a day or so).

There may be a couple of places to set the cache-control headers. The headers could be set in the php code, or by nginx. There are advantages and disadvantages to each approach. Php code can provide greater flexibility to headers if different pages need different settings. It may require some more complex code to be written. Using nginx is usually a simple configuration, which can be good for things like static assets (javascript, css, images) that don’t need to be processed by the php process. A hybrid approach may be needed to get the best results.