缓存类增加tag方法 用于缓存标签设置 clear方法支持清除某个缓存标签的数据

library/think/cache/driver/Memcached.php

@@ -11,7 +11,9 @@
 
 namespace think\cache\driver;
 
-class Memcached
+use think\cache\Driver;
+
+class Memcached extends Driver
 {
     protected $handler;
     protected $options = [
@@ -98,9 +100,13 @@ class Memcached
         if (is_null($expire)) {
             $expire = $this->options['expire'];
         }
+        if ($this->tag && !$this->has($name)) {
+            $first = true;
+        }
         $name   = $this->options['prefix'] . $name;
         $expire = 0 == $expire ? 0 : $_SERVER['REQUEST_TIME'] + $expire;
         if ($this->handler->set($name, $value, $expire)) {
+            isset($first) && $this->setTagItem($name);
             return true;
         }
         return false;
@@ -155,10 +161,17 @@ class Memcached
     /**
      * 清除缓存
      * @access public
+     * @param string $tag 标签名
      * @return bool
      */
-    public function clear()
+    public function clear($tag = null)
     {
+        if ($tag) {
+            // 指定标签清除
+            $keys = $this->getTagItem($tag);
+            $this->handler->deleteMulti($keys);
+            return true;
+        }
         return $this->handler->flush();
     }
 }