Merge pull request #8298 from cakephp/4.x-apcu-engine

add ApcuEngine options section

Author: markstory

docs/en/core-libraries/caching.md

@@ -159,6 +159,17 @@ FileEngine uses the following engine specific options:
 - `mask` The mask used for created files
 - `path` Path to where cachefiles should be saved. Defaults to system's temp dir.
 
+### ApcuEngine Options
+
+ApcuEngine does not have any engine specific options. It requires the
+[APCu](https://php.net/apcu) extension to be installed and enabled.
+
+Because APCu stores values in the local webserver process shared memory, it is
+best suited for data that can be regenerated and does not need to be shared
+between servers. When clearing cache data, ApcuEngine removes entries matching
+the cache configuration's `prefix`, so use unique prefixes for each cache
+configuration that uses APCu.
+
 <a id="caching-redisengine"></a>
 
 ### RedisEngine Options