wowrdpress_cache_fetch.php

<?php
function cache_fetch($key, $group='', $callable, $expiration=0) {
  $value = wp_cache_get($key, $group);
  if(!$value) {
    $value = $callable();
    wp_cache_set($key, $value, $group, $expiration);
  }
  return $value;
}


cache_fetch("recent_post_ids", "", function() {
  return "code tha calculates value(s) to cache";
}, 60 * 60 * 24);