title: Laravel validation rule "different"
body: <p>I am having a hard time understanding this validation rule. Basically, I have two fields, and they are both <code>nullable</code>. But, once both fields are filled, they have to be different from each other. I cannot enter <code>test</code> in both of them, for example. This validation rule works, if I fill <code>both</code> fields.</p>
  
  <p>But, when I only fill <code>one</code> of the fields, the validation fails and says the fields should be different from each other with the following message:</p>
  
  <pre><code>The name and replace must be different.
  </code></pre>
  
  <p>I checked what is being submitted to my Form Request, and this is the following:</p>
  
  <pre><code>"name" =&gt; null
  "replace" =&gt; "test"
  </code></pre>
  
  <p>Stripped version of my validation rules:</p>
  
  <pre><code>public function rules()
  {
      return [
          'name' =&gt; 'different:replace|nullable',
          'replace' =&gt; 'different:name|nullable',
      ];
  }
  </code></pre>
  
  <p>Can somebody explain to me what I am misunderstanding with this validation rule? Do <code>null</code> values not count with this rule?</p>