zendframework/zf2 — pull request #4629 by weierophinney (2013-06-11 20:40:29+00:00)
Title: Zend\Cache\Pattern\CallbackCache doesn't work with NULL

https://github.com/zendframework/zf2/blob/master/library/Zend/Cache/Pattern/CallbackCache.php#L51

if (!isset($result[0])) {
throw new Exception\RuntimeException("Invalid cached data for key '{$key}'");
}

The cache has been saved and loaded correct but this condition returns false because isset returns false on NULL - should be replaced by array_key_exists

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