Developers which are used to the admin generator are used of the functionality how this admin genereator sorts a list.

In the th tag of the list, there is used something like this:

          <?php if ($sf_user->getAttribute('sort', null, 'sf_admin/news/sort') == 'is_published'): ?>
      <?php echo link_to(__('Is published'), 'news/list?sort=is_published&type='.($sf_user->getAttribute('type', 'asc', 'sf_admin/news/sort') == 'asc' ? 'desc' : 'asc')) ?>
      (<?php echo __($sf_user->getAttribute('type', 'asc', 'sf_admin/news/sort')) ?>)
      <?php else: ?>
      <?php echo link_to(__('Is published'), 'news/list?sort=is_published&type=asc') ?>
      <?php endif; ?>

This is pretty hard to read and i have put this stuff of code in a helper method:

/**
 * This helper function does exactly the same code output than
 * ---------
 *           <?php if ($sf_user->getAttribute('sort', null, 'sf_admin/news/sort') == 'is_published'): ?>
 *     <?php echo link_to(__('Is published'), 'news/list?sort=is_published&type='.($sf_user->getAttribute('type',   'asc', 'sf_admin/news/sort') == 'asc' ? 'desc' : 'asc')) ?>
 *     (<?php echo __($sf_user->getAttribute('type', 'asc', 'sf_admin/news/sort')) ?>)
 *     <?php else: ?>
 *     <?php echo link_to(__('Is published'), 'news/list?sort=is_published&type=asc') ?>
 *     <?php endif; ?>
 * ---------
  * 
 * @author Frank Stelzer
 * 
 * @param string $name
 * @param string $base_internal_uri
 * @param string $sort_name
 * @param string $ns the name space
 * @return string html code
 */
function sortable_link_to($name, $base_internal_uri = '', $sort_name = '', $ns = ''){
    $retval = '';
 
    $sort_name = $sort_name=='' ? $name : $sort_name;
 
    $user = sfContext::getInstance()->getUser();
    /*@var $user sfBasicSecurityUser */
 
    if ($user->getAttribute('sort', null, $ns) == $sort_name){
        $retval .= link_to($name, $base_internal_uri.(strpos($base_internal_uri,'?')? '&' : '?'). 'sort='.$sort_name.'&type='.($user->getAttribute('type', 'asc', $ns) == 'asc' ? 'desc' : 'asc'));
        $retval .=show_sort_type($user->getAttribute('type', 'asc', $ns));
    }else {
        $retval = link_to($name, $base_internal_uri.(strpos($base_internal_uri,'?')? '&' : '?'). 'sort='.$sort_name.'&type=asc');
    }
 
    return $retval;
}
 
 
/**
 * helper function which is used in the sortable_link_to function
 *
 * @author Frank Stelzer
 *
 * @param string $type
 * @return string html code
 */
function show_sort_type($type){
    $t=$type=='asc'? '&darr;' : '&uarr;';
    // return " ($t) ";
    return " $t ";
}

You can put in the show_sort_type whatever you want. You can display some arrow images or other stuff....

So, when you have a list/table, which you want to sort, you only have to put this code above in a helper and to write this in a template:

echo sortable_link_to(__('Content'),'module/action'),'content', 'module/action/sort');

This is much better to read than the first code, or? :)

Look in generated action code of the admin generator to see how one has to use an incoming sort request.

These methods are mainly used:

    protected function addSortCriteria($c)
    {
        if ($sort_column = $this->getUser()->getAttribute('sort', null, 'namespace'))
        {
            $sort_column = CustomPeer::translateFieldName($sort_column, BasePeer::TYPE_FIELDNAME, BasePeer::TYPE_COLNAME);
            if ($this->getUser()->getAttribute('type', null, 'namespace') == 'asc')
            {
                $c->addAscendingOrderByColumn($sort_column);
            }
            else
            {
                $c->addDescendingOrderByColumn($sort_column);
            }
        }
    }
 
    protected function processSort()
    {
        if ($this->getRequestParameter('sort'))
        {
            $this->getUser()->setAttribute('sort', $this->getRequestParameter('sort'), 'namespace');
            $this->getUser()->setAttribute('type', $this->getRequestParameter('type', 'asc'), 'namespace');
        }
 
        if (!$this->getUser()->getAttribute('sort', null, 'namespace'))
        {
        }
    }

In Your custom action you than need:

        $this->processSort();
 
        $c=new Criteria();
        $this->addSortCriteria($c);
// your other criterias here