如何在Laravel中的验证规则之间进行OR运算？

public function rules()
{
    return [
        'name' => 'required|string',
        'email' => 'required|email',
        'phone' => 'required|numeric',
        'password' => 'required|string|min:8',
        'password_confirmation' => 'required|string|same:password',
        'age' => 'required|integer|min:18',
        'gender' => 'required|string|in:male,female',
        'terms' => 'required|accepted',
        'newsletter' => 'nullable|boolean',
        'avatar' => 'nullable|image|max:2048',
    ];
}