/**
  * ZADD key [NX|XX] [CH] [INCR] score member [score member ...]
  * Available since 1.2.0.
  * Time complexity: O(log(N)) for each item added, where N is the number of elements in the sorted set.
  * @link http://redis.io/commands/zadd
  *
  * @param string $key
  * @param array $members array(member => score [, member => score ...])
  * @param string|null $nx NX or XX
  * @param bool|false $ch
  * @param bool|false $incr
  * @return int|string
  */
 public function zadd($key, array $members, $nx = null, $ch = false, $incr = false)
 {
     $params = [$key];
     if ($nx) {
         $params[] = $nx;
     }
     if ($ch) {
         $params[] = 'CH';
     }
     if ($incr) {
         $params[] = 'INCR';
     }
     $params[] = Parameter::assocArrayFlip($members);
     return $this->returnCommand(['ZADD'], $params);
 }
 /**
  * ZADD key score member [score member ...]
  * Available since 1.2.0.
  * Time complexity: O(log(N)) for each item added, where N is the number of elements in the sorted set.
  * @link http://redis.io/commands/zadd
  *
  * @param string $key
  * @param array $members array(member => score [, member => score ...])
  * @return int|string
  */
 public function zadd($key, array $members)
 {
     return $this->returnCommand(['ZADD'], [$key, Parameter::assocArrayFlip($members)]);
 }