var originalContent;

function displayInfo(id)
{
  var s = 'id=' + id;
  
  new Ajax.Request('info.php', 
  {
    parameters: s, 
    method: "post",
    onSuccess:function(response) 
    {
      var node = $('photo-info-' + id);
      originalContent = node.innerHTML;
      node.innerHTML = response.responseText;
    }, 
    onFailure:function(response) 
    {
      alert('Error: ' + response.status + ' ' + response.statusText);
    }
  });
}

function hideInfo(id)
{
  // Restore original content
  var node = $('photo-info-' + id);    
  // remove all children
  while (node.firstChild != null)
  {
    node.removeChild(node.firstChild);
  }
  node.innerHTML = originalContent;
}