Drupal 7 temporary cache item won't expire

I have a fairly expensive server call that I need to cache for 30 seconds. It seems however that I can not get the cache to expire.

In the code below, after the first time it caches, it will never get past $return->cache_data, even after the time() + 30 seconds.

Note, I can even print $cache->expire and it is definitely set to a time past 30 seconds ago and never updates.

I've manually cleared cache many times to confirm I get the same results.

Does anything look wrong with this?

function mymodule_get_something($id) {
// set the unique cache id
$cid = 'id-'. $id;

// return data if there's an un-expired cache entry
// *** $cache ALWAYS gets populated with my expired data
if ($cache = cache_get($cid, 'cache_mymodule')) {
return $cache->data;
}

// set my super expensive data call here
$something = array('Double Decker Taco', 'Burrito Supreme');

// set the cache to expire in 30 seconds
cache_set($cid, $something, 'cache_mymodule', time() + 30);

// return my data
return $something;
}

There's nothing wrong with your code as such, I think the problem is in how `cache_set` behaves. From the [docs page](

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), passing a UNIX timestamp:

> Indicates that the item should be kept at least until the given time, after which it behaves like CACHE_TEMPORARY.

`CACHE_TEMPORARY` behaves like this:

> Indicates that the item should be removed at the next general cache wipe.

My best guess is that because you're not implicitly forcing that general cache wipe (using [`cache_clear_all()`](

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)) the cache object will persist.

I think a simple way around it would just be to manually test the expiry time after your cache check, and let it fall through to re-setting that cache object if it has expired:

if ($cache = cache_get($cid, 'cache_mymodule')) {
if ($cache->expire > REQUEST_TIME) {
return $cache->data;
}
}