src/Leevel/Http/Bag.php
public function has(string $key): bool
    {
        $key = $this->normalize($key);

        return array_key_exists($key, $this->elements);
    }
public function has(string $key): bool
    {
        $key = $this->normalize($key);

        return array_key_exists($key, $this->elements);
    }
判断是否存在元素值

@param string $key

@return bool