laravel仅在存在另一个值时才会生效

Question

I want to validate a field only if another field is present.

This is my current implementation that can illustrate what I want to do. I need to perform unique validation on campaign_lead_id only if campaign_id is present. Other wise, there will be query exception thrown because $params['campaign_id'] is empty.

    $params = [
        'campaign_id' => '',
        'campaign_lead_id' => '23'
    ];

    $customCampaignLeadRule = (empty($params['campaign_id'])
        ? ''
        : '|unique:leads,campaign_lead_id,null,id,campaign_id,' . $params['campaign_id']
    );

    $rules = [
        'campaign_id' => 'required',
        'campaign_lead_id' => 'bail|required' . $customCampaignLeadRule,
    ];

    $validator = $this->validator->make($params, $rules);

P.S. I am aware of bail and required_if. What I need is not required_if because I always require campaign_lead_id not only when other field is required. My implementation works for me but I think it is not the most correct way.