$( "li[id^='panel']" ).hide();

    $( "p[id^='panelopen']" ).on('click', function (event){
                $( "li[id^='panel']" ).toggle();
    });


     <li class="row bars">
      <div class="col-sm-1 btn btn-secondary">
        <p id="panelopen$i">details</p>
      </div>
    </li>
    <li id="panel" class="row">
      <div class="col-sm-1"></div>
      <div class="col-sm-5">
         <textarea type="text" name="description">'; echo
   $row['description']; echo'</textarea>
      </div>
    </li> ';