function show_review_form(){
  document.getElementById('review_form').style.display = '';
  document.getElementById('hide_review_form').style.display = '';
  document.getElementById('review_form_add').style.display = '';
  document.getElementById('add_review').style.display = 'none';
}

function hide_review_form(){
  document.getElementById('review_form').style.display = 'none';
  document.getElementById('hide_review_form').style.display = 'none';
  document.getElementById('review_form_add').style.display = 'none';
  document.getElementById('add_review').style.display = '';
}