- $value = $memcache->get(get_app()->get_hostname().":".$key);
- if (!is_bool($value)) {
- return unserialize($value);
+ $cached = $memcache->get(get_app()->get_hostname().":".$key);
+ $value = @unserialize($cached);
+
+ // Only return a value if the serialized value is valid.
+ // We also check if the db entry is a serialized
+ // boolean 'false' value (which we want to return).
+ if ($cached === serialize(false) || $value !== false) {
+ return $value;