fix: Enhance Redis caching to support scalars cached as plain strings

system/libraries/Cache/drivers/Cache_redis.php

@@ -162,16 +162,16 @@ public function __construct()
 	public function get($key)
 	{
 		$data = $this->_redis->hMGet($key, array('__ci_type', '__ci_value'));
-
-		if ($this->_redis->sIsMember('_ci_redis_serialized', $key))
+		// Also serves scalars that 3.1.x cached as plain strings
+		if ($data === FALSE)
 		{
-			return FALSE;
+			return $this->_get_v31($key);
 		}
 
-		// Also serves scalars that 3.1.x cached as plain strings
-		if ($data === FALSE)
+		// Key doesn't exist (hMGet returns an array of FALSE values)
+		if ( ! isset($data['__ci_type'], $data['__ci_value']) OR $data['__ci_value'] === FALSE)
 		{
-			return $this->_redis->get($key);
+			return FALSE;
 		}
 
 		switch ($data['__ci_type'])
@@ -295,14 +295,15 @@ public function decrement($id, $offset = 1)
 	 */
 	protected function _increment($id, $offset)
 	{
-		$value = $this->_redis->incrBy($id, $offset);
-
-		if ($value === FALSE)
+		// Also serves scalars that 3.1.x cached as plain strings, incrBy creates the key if not existing
+		if ($this->_redis->type($id) === Redis::REDIS_STRING)
 		{
-			$value = $this->_redis->hIncrBy($id, '__ci_value', $offset);
-			$value === FALSE OR $this->_redis->hSet($id, '__ci_type', 'integer');
+			return $this->_redis->incrBy($id, $offset);
 		}
 
+		$value = $this->_redis->hIncrBy($id, '__ci_value', $offset);
+		$value === FALSE OR $this->_redis->hSet($id, '__ci_type', 'integer');
+
 		return $value;
 	}
 
@@ -386,4 +387,24 @@ public function __destruct()
 			$this->_redis->close();
 		}
 	}
+
+	// ------------------------------------------------------------------------
+
+	/**
+	 * Get scalars that 3.1.x cached as plain strings
+	 *
+	 * @param	string	$key	Cache ID
+	 * @return	mixed
+	 */
+	private function _get_v31($key)
+	{
+		$value = $this->_redis->get($key);
+
+		if ($value !== FALSE && $this->_redis->sIsMember('_ci_redis_serialized', $key))
+		{
+			return unserialize($value);
+		}
+
+		return $value;
+	}
 }