There are two things involved mainly. Firstly, grabbing the page's uri which you might use $_SERVER['REQUEST_URI'] as a starting point. Secondly, to grab the page's finished HTML you would want to use output buffering with a callback function/method to save a cache file.
Of course, things can be made much more complex if you wish or if your requirements dictate it.
The Following User Says Thank You to Salathe For This Useful Post:
That makes me feel better as one of the main reasons I was going to go with Drupal was because of page caching.. but if I can get page caching built in at a later date on more of a custom route that's good news.
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