For ergonomic and graphism reasons, I sometimes prefer to use link rather than buttons and/or button rather than links...

To do so, I created this small function :

<?php
# File : JsHelper.php
 
// use of "normal" Javascript Helper
use_helper('Javascript');
 
 
/*!
 * Create a link that submit the closest parent form
 *
 * @param $string    string : text to display
 * @param $options mixed : options to be pass to the tag
 * @return string                : HTML code for the link
 */
function link_to_submit( $string, $options = null )
{
  $func = ";var a=this.ancestors();for(var i in a){if(a[i].tagName=='FORM'){try{a[i].onsubmit();} catch(err){a[i].submit();}break;}}";
  return link_to_function( $string, $func, $options );
}
 
 
 
/*!
 * Create a button that act as a link
 *
 * @param $string    string : text to display in the button
 * @param $url         string : URL of the link
 * @param $options mixed : options to be pass to the tag
 * @return string                : HTML code for the link
 */
function button_to_link( $string, $url, $options = null )
{
  $url = url_for($url);
 
  $func = ";document.location = '$url';return false;";
  if ( is_string($options) ) $options.= " onclick=$func";
  else $options['onclick'] = $func;
 
  return tag('button', $options ).htmlspecialchars($string).'</button>';
}
 

Then, you simply use it as a normal link_to function :

<? use_helper('Js') ?>
 
<?=form_tag('module/action')?>
  <?=input_tag('text')?>
  <?=link_to_submit('Validate')?>
  <?=link_to('Cancel','module/index')?>
</form>
 

Or :

<? use_helper('Js') ?>
 
<?=form_tag('module/action')?>
  <?=input_tag('text')?>
  <?=submit_tag('Validate')?>
  <?=button_to_link('Cancel','module/index')?>
</form>
 

In these two examples, links/buttons of the form are graphicly consistents. For a better user experience ;)

PS : works as well with AJAX forms form_remote_tag()

PPS : Don't forget that thanks to CSS, you can make a button looking like a link (et vice-versa).

PPPS : Don't forget that buttons and links doesn't have the same meaning for search engine bots.

PPPPS : Don't forget that this rely on the fact that user is using javascript!!!

Here is how I did this... Create a sfGuardAuth module in your application and edit the actions.class.php file as follow.

The trick is to not try to overwrite the sfGuardAuth/signin action, as it use validation. As well it allow you to use the "normal" signin way (form and etc).

require_once(sfConfig::get('sf_plugins_dir').'/sfGuardPlugin/modules/sfGuardAuth/lib/BasesfGuardAuthActions.class.php');
 
class sfGuardAuthActions extends BasesfGuardAuthActions
{
  public function executeHTTPSignin()
  {
    // get somme interesting stuff!
    $request = $this->getRequest();
    $response = $this->getResponse();
    $user = $this->getUser();
 
    // An HTTP authenticated user cannot logout (browser always send authentification datas)
    // So we must be sure that the user has seen the HTTP authentification box before
    if ( $user->getAttribute('request_authentification') )
    {
      // If authentification datas has been sent
      if ( isset( $_SERVER['PHP_AUTH_USER'], $_SERVER['PHP_AUTH_PW'] ) )
      {
        // If correct username given
        $guarduser = sfGuardUserPeer::retrieveByUserName( $_SERVER['PHP_AUTH_USER'] );
        if ( $guarduser instanceof sfGuardUser )
        {
          // If correct Password given
          if ( ($guarduser instanceof sfGuardUser) and ($guarduser->checkpassword( $_SERVER['PHP_AUTH_PW'] )) )
          {
            // we can signin the user and redirect it
            $user->signin( $guarduser );
            $user->setAttribute('request_authentification',false);
            $this->redirect( sfConfig::get('app_sf_guard_plugin_success_signin_url','@homepage') );
            throw new sfStopException;
          }
        }
      }
    }
 
    // else, popup the authentification box
    $user->setAttribute('request_authentification',true);
    $response->setHttpHeader( 'WWW-Authenticate', 'Basic realm="Identification"' );
    $response->setHttpHeader( 'HTTP/1.0', '401 Unauthorized' );
 
    // This will be displayed if the user cancel the authentification process
    $this->forward( 'sfGuardAuth', 'password' );
    throw new sfStopException;
  }
 
  public function executePasswowd()
  {
    # Implement this action as usual...
  }
}
 

Enjoy... (I hope)