That's the question!

There's not much explanation on wp_cache_set() an even less for wp_cache_add().

What should I use in which circumstances?

1 Answer 1


According with WP Object API documentation both functions accepts these arguments:

  • $key: the key to indicate the value.
  • $data: the value you want to store.
  • $group: (optional) this is a way of grouping data within the cache. Allows you to use the same key across different groups.
  • $expire: (optional) this defines how many seconds to keep the cache for. Only applicable to some functions. Defaults to 0 (as long as possible).

The difference is:

  • wp_cache_add(): if the cache key doesn't exist, it add the cache data. If the cache key already exists, the function returns false and does nothing with the cached data.
  • wp_cache_set(): same as above but if the cache key already exists, the cache data is overwritten.
  • 2
    and why didn't I RTFM? Thank you!
    – Xaver
    Oct 21, 2015 at 9:23

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