I am tweaking a zen-cart website to be more cpu efficient. After profiling it, I see that the getimagesize function is accounting for nearly 50% of page load time. The images are locally stored. One option is to go through zen-cart's source code and replace this function with something custom to reference a cached value since images are rarely ever changed. However, since php is open source, perhaps another option is available: Is there any way to modify this function to make it just read a value from a cache which I can set whenever I upload an image to the server? Maybe by adding an optional parameter to the function that makes it read from cache.
Interesting idea, but this would require recompiling PHP. While not impossible, it's probably not a good idea from a maintenance point of view: You would have to re-integrate your patch on every PHP update.
However, you might be able to override getimagesize(): There seem to be PHP modules and libraries that can add this capability to PHP.
I have no experience with any of them, but here are some suggestions on how to do it: