Think/Cache/Driver/Memcached.php
public function set($name, $value, $expire = null)
    {
//            N('cache_write', 1);
        if (is_null($expire)) {
            $expire = $this->options['expire'];
        }
        $name = $this->options['prefix'].$name;
        if ($this->handler->set($name, $value, time() + $expire)) {
            if ($this->options['length'] > 0) {
                // 记录缓存队列
                $this->queue($name);
            }

            return true;
        }

        return false;
    }
public function set($name, $value, $expire = null)
    {
//            N('cache_write', 1);
        if (is_null($expire)) {
            $expire = $this->options['expire'];
        }
        $name = $this->options['prefix'].$name;
        if ($this->handler->set($name, $value, time() + $expire)) {
            if ($this->options['length'] > 0) {
                // 记录缓存队列
                $this->queue($name);
            }

            return true;
        }

        return false;
    }
写入缓存

@param string $name 缓存变量名
@param mixed $value 存储数据
@param int $expire 有效时间（秒）

@return bool