Mention PhpRedis and false negatives.

cache.md

@@ -63,7 +63,7 @@ You may also set the `host` option to a UNIX socket path. If you do this, the `p
 
 #### Redis
 
-Before using a Redis cache with Laravel, you will need to install the `predis/predis` package (~1.0) via Composer.
+Before using a Redis cache with Laravel, you will need to either install the `predis/predis` package (~1.0) via Composer, or install the PhpRedis PHP extension via PECL.
 
 For more information on configuring Redis, consult its [Laravel documentation page](/docs/{{version}}/redis#configuration).
 
@@ -168,6 +168,8 @@ Instead of passing the number of minutes as an integer, you may also pass a `Dat
 
     Cache::put('key', 'value', $expiresAt);
 
+> {note} Storing `false` or `null` values will lead to false negatives, because Laravel treats both as a null value.
+
 #### Store If Not Present
 
 The `add` method will only add the item to the cache if it does not already exist in the cache store. The method will return `true` if the item is actually added to the cache. Otherwise, the method will return `false`: