缓存驱动统一增加handler方法用于获取操作对象的句柄（某些缓存类型可能为null）

library/think/cache/Driver.php

@@ -16,6 +16,7 @@ namespace think\cache;
  */
 abstract class Driver
 {
+    protected $handler = null;
     protected $options = [];
     protected $tag;
 
@@ -173,4 +174,15 @@ abstract class Driver
             return [];
         }
     }
+
+    /**
+     * 返回句柄对象，可执行其它高级方法
+     *
+     * @access public
+     * @return object
+     */
+    public function handler()
+    {
+        return $this->handler;
+    }
 }

library/think/cache/driver/Memcache.php

@@ -16,7 +16,6 @@ use think\Exception;
 
 class Memcache extends Driver
 {
-    protected $handler = null;
     protected $options = [
         'host'       => '127.0.0.1',
         'port'       => 11211,

library/think/cache/driver/Memcached.php

@@ -15,7 +15,6 @@ use think\cache\Driver;
 
 class Memcached extends Driver
 {
-    protected $handler;
     protected $options = [
         'host'     => '127.0.0.1',
         'port'     => 11211,

library/think/cache/driver/Redis.php

@@ -22,7 +22,6 @@ use think\cache\Driver;
  */
 class Redis extends Driver
 {
-    protected $handler = null;
     protected $options = [
         'host'       => '127.0.0.1',
         'port'       => 6379,
@@ -174,14 +173,4 @@ class Redis extends Driver
         return $this->handler->flushDB();
     }
 
-    /**
-     * 返回句柄对象，可执行其它高级方法
-     *
-     * @access public
-     * @return object
-     */
-    public function handler()
-    {
-        return $this->handler;
-    }
 }

library/think/cache/driver/Sqlite.php

@@ -20,7 +20,6 @@ use think\Exception;
  */
 class Sqlite extends Driver
 {
-
     protected $options = [
         'db'         => ':memory:',
         'table'      => 'sharedmemory',

library/think/cache/driver/Wincache.php

@@ -25,8 +25,6 @@ class Wincache extends Driver
         'expire' => 0,
     ];
 
-    protected $tag;
-
     /**
      * 架构函数
      * @param array $options 缓存参数