title: Using multiple required_if in a validation rule
body: <p>I have a <code>select</code> with many options, I want another <code>select</code> to be required when the first has an specific value.</p>
  
  <pre><code>    &lt;select id="category" name="category"&gt;
              &lt;option value="a"&gt;Option A&lt;/option&gt;
              &lt;option value="b"&gt;Option B&lt;/option&gt;
              &lt;option value="c"&gt;Option C&lt;/option&gt;
              &lt;option value="d"&gt;Option D&lt;/option&gt;
              &lt;option value="e"&gt;Option E&lt;/option&gt;
              &lt;option value="f"&gt;Option F&lt;/option&gt;
      &lt;/select&gt;
  
      &lt;select id="subcategory" name="subcategory"&gt;
              &lt;option value="a"&gt;Suboption A &lt;/option&gt;
              &lt;option value="b"&gt;Suboption B &lt;/option&gt;
              &lt;option value="c"&gt;Suboption C &lt;/option&gt;
              &lt;option value="d"&gt;Suboption D &lt;/option&gt;
              &lt;option value="e"&gt;Suboption E &lt;/option&gt;
      &lt;/select&gt;
  </code></pre>
  
  <p>I want the second <code>select</code> to be required when the user chooses option a,b or f. Is it correct to use the next rule in the controller code that validates the inputs?:</p>
  
  <pre><code>    $rules = array(
              'category' =&gt; 'alpha|in:a,b,c,d,e,f|required|size:1',
              'subcategory' =&gt; 'alpha|
                                in:a,b,f|
                                required_if:category,a|
                                required_if:category,b|
                                required_if:category,f|
                                size:1'
      );
  </code></pre>
  
  <p>Is there (another or) a better way to validate this?</p>