* It is generally preferable to use a class constant when setting this value.
* This has no effect unless pcTTL is used.
* Default: WANObjectCache::PC_PRIMARY.
- * - version: Integer version number. This allows for callers to make breaking changes to
- * how values are stored while maintaining compatability and correct cache purges. New
- * versions are stored alongside older versions concurrently. Avoid storing class objects
- * however, as this reduces compatibility (due to serialization).
+ * - version: Integer version number. This lets callers make breaking changes to the format
+ * of cached values without causing problems for sites that use non-instantaneous code
+ * deployments. Old and new code will recognize incompatible versions and purges from
+ * both old and new code will been seen by each other. When this method encounters an
+ * incompatibly versioned value at the provided key, a "variant key" will be used for
+ * reading from and saving to cache. The variant key is specific to the key and version
+ * number provided to this method. If the variant key value is older than that of the
+ * provided key, or the provided key is non-existant, then the variant key will be seen
+ * as non-existant. Therefore, delete() calls invalidate the provided key's variant keys.
+ * The "checkKeys" and "touchedCallback" options still apply to variant keys as usual.
+ * Avoid storing class objects, as this reduces compatibility (due to serialization).
* Default: null.
* - minAsOf: Reject values if they were generated before this UNIX timestamp.
* This is useful if the source of a key is suspected of having possibly changed