Fixed php compile error

Author: Geolim4

src/phpFastCache/Drivers/Couchbase/Driver.php

@@ -26,16 +26,12 @@
 /**
  * Class Driver
  * @package phpFastCache\Drivers
+ * @property CouchbaseClient $instance Instance of driver service
  */
 class Driver implements ExtendedCacheItemPoolInterface
 {
     use DriverBaseTrait;
 
-    /**
-     * @var CouchbaseClient
-     */
-    public $instance;
-
     /**
      * @var \CouchbaseBucket[]
      */

src/phpFastCache/Drivers/Leveldb/Driver.php

@@ -26,18 +26,14 @@
 /**
  * Class Driver
  * @package phpFastCache\Drivers
+ * @property LeveldbClient $instance Instance of driver service
  */
 class Driver implements ExtendedCacheItemPoolInterface
 {
     use DriverBaseTrait, IOHelperTrait;
 
     const LEVELDB_FILENAME = '.database';
 
-    /**
-     * @var LeveldbClient Instance of driver service
-     */
-    public $instance;
-
     /**
      * Driver constructor.
      * @param array $config

src/phpFastCache/Drivers/Ssdb/Driver.php

@@ -27,15 +27,11 @@
 /**
  * Class Driver
  * @package phpFastCache\Drivers
+ * @property SimpleSSDB $instance Instance of driver service
  */
 class Driver implements ExtendedCacheItemPoolInterface
 {
     use DriverBaseTrait;
-    
-    /**
-     * @var SimpleSSDB
-     */
-    public $instance;
 
     /**
      * Driver constructor.