Multiselect value in wp_query

Question

i have been trying to display the post that contain specific tag.

what i am trying is: if user search for post related to tagss for example: if user selects the tag Don after submition the query will fetch post that contains don tag.

for that i have created one multiselect form. user will select multiple tags. for exapmle mama and don.

after form submit getting array of multiple selected values like:

     array([0]=>11,[1]=>18)
      $options = $_post['options'];
 i am passing this values to new WP_Query( array( 'tag__in' => array( $options ) ) );  


  <form method="post" action="" multiple="multiple">

   <select name="options[]" multiple="multiple">
       <option value="15">mama</option>
       <option value="16">chacha</option>
       <option value="17">Bhatija</option>
       <option value="18">Don</option>
   </select>

  <input type="submit" value="submit" name="submit"/> 
  </form>

      <?php 

            if(isset($_POST['submit'])):

   $options = $_POST['options'];

   $query = new WP_Query( array( 'tag__in' => array( $options ) ) ); 
  //print_r($query);

  while ($query->have_posts()) : $query->the_post(); 

    echo get_the_tile($post->ID);

   endwhile;

unfortunately it is not working.

need help to get the list of post by selected tag.