src/Leevel/Session/Session.php
public function flash(string $key, $value): void
    {
        $this->set($this->flashDataKey($key), $value);

        $this->mergeNewFlash([
            $key,
        ]);

        $this->popOldFlash([
            $key,
        ]);
    }
public function flash(string $key, $value): void
    {
        $this->set($this->flashDataKey($key), $value);

        $this->mergeNewFlash([
            $key,
        ]);

        $this->popOldFlash([
            $key,
        ]);
    }
闪存一个数据，当前请求和下一个请求可用.

@param string $key
@param mixed  $value