How can i get a email from Symfony when a log message is prune?

<?php
 
/**
 * gfMailLogger logs messages and send it via email.
 *
 * @package    symfony
 * @subpackage log
 * @author     Gordon Franke <gfranke@nevalon.de>
 * @link       http://www.nevalon.de
 */
class gfMailLogger extends sfLogger
{
  protected
    $emails     = array(),
    $subject,
    $body,
    $include_level,
    $log = false,
    $type       = 'symfony',
    $format     = '%time% %type% [%priority%] %message%%EOL%',
    $timeFormat = '%b %d %H:%M:%S';
 
  /**
   * Initializes this logger.
   *
   * Available options:
   *
   * - emails:        The emails to be send the log messages
   * - subject:       The subject for the email
   * - include_level: Use this to get more detailed information
   * - format:        The log line format (default to %time% %type% [%priority%] %message%%EOL%)
   * - time_format:   The log time strftime format (default to %b %d %H:%M:%S)
   *
   * @param  sfEventDispatcher $dispatcher  A sfEventDispatcher instance
   * @param  array             $options     An array of options.
   *
   * @return Boolean      true, if initialization completes successfully, otherwise false.
   */
  public function initialize(sfEventDispatcher $dispatcher, $options = array())
  {
    if (!isset($options['emails']))
    {
      throw new sfConfigurationException('You must provide a "emails" parameter for this logger.');
    }
    $this->emails = $options['emails'];
 
    if (isset($options['format']))
    {
      $this->format = $options['format'];
    }
 
    if (isset($options['time_format']))
    {
      $this->timeFormat = $options['time_format'];
    }
 
    if (isset($options['type']))
    {
      $this->type = $options['type'];
    }
 
    if (isset($options['subject']))
    {
      $this->subject = $options['subject'];
    }
    else
    {
      $this->subject = sfConfig::get('sf_app') . ':: Log';
    }
 
    parent::initialize($dispatcher, $options);
 
    if (isset($options['include_level']))
    {
      if (!is_int($options['include_level']))
      {
        $options['include_level'] = constant('sfLogger::'.strtoupper($options['include_level']));
      }
 
      $this->include_level = $options['include_level'];
    }
    else
    {
      $this->include_level = $this->getLogLevel();
    }
  }
 
  /**
   * Logs a message.
   *
   * @param string $message   Message
   * @param string $priority  Message priority
   */
  public function log($message, $priority = self::INFO)
  {
    if ($this->include_level < $priority)
    {
      return false;
    }
    if($this->getLogLevel() >= $priority)
    {
      $this->log = true;
    }
 
    return $this->doLog($message, $priority);
  }
 
  /**
   * Logs a message.
   *
   * @param string $message   Message
   * @param string $priority  Message priority
   */
  protected function doLog($message, $priority)
  {
    $this->body .= strtr($this->format, array(
      '%type%'     => $this->type,
      '%message%'  => $message,
      '%time%'     => strftime($this->timeFormat),
      '%priority%' => $this->getPriority($priority),
      '%EOL%'      => PHP_EOL,
    ));
  }
 
  /**
   * Returns the priority string to use in log messages.
   *
   * @param  string $priority The priority constant
   *
   * @return string The priority to use in log messages
   */
  protected function getPriority($priority)
  {
    return sfLogger::getPriorityName($priority);
  }
 
  /**
   * Executes the shutdown method.
   */
  public function shutdown()
  {
    if($this->log)
    {
      foreach($this->emails as $email)
      {
        mail($email, $this->subject, $this->body);
      }
    }
  }
}