title: wp dropdown categories selected value
body: <p>I'm writing a shorcode API function. I want to save the selected value from the <code>wp_dropdown_categories</code> to use that value in the <code>wp_query</code>.</p>
  
  <pre><code>echo `&lt;form action="" method="POST"&gt;`;
    $values = array(
      `orderby` =&gt; `name`, 
      `order` =&gt; `ASC`,
      `echo` =&gt; 1,
      `selected` =&gt; $kat = get_query_var( `cat` ),
      `name` =&gt; 'cat',
      `id` =&gt; ``,
      `taxonomy` =&gt; `persons`
    );
    wp_dropdown_categories( $values );
   echo `&lt;input type="submit" name="submit" value="view" /&gt;;
  echo `&lt;/form&gt;`;
  </code></pre>
  
  <p>I want to use the selected value to search in the custom taxonomy</p>
  
  <pre><code>$args = array(
    `post_type` =&gt; `client`,
    `persons` =&gt; `here selected value from wp_dropdown_categories`
  );
  $my_query = new WP_Query( $args );
  
  if( $my_query-&gt;have_posts() ) {
    echo `Name: `;
    while ($my_query-&gt;have_posts()) : $my_query-&gt;the_post();
    echo the_title();
    endwhile;
  }
  </code></pre>