$string = preg_replace_callback('#\[youtube(=(.+?)|)\].+?youtube.com/watch\?v=(.+?)(&.+?|)\[/youtube\]#is', array($this, 'youtube'), $string);

function youtube($matches) {
$title = ($matches[2] !== '') ? '<b>'.$matches[2].'</b><br>' : '';
return $title.'<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/'.$matches[3].'&hl=ru&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/'.$matches[3].'&hl=ru&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object><br>';
}

$this->LANG['SpoilerShow'] = '<img src="./templates/'.DEF_SKIN.'/im/up.gif" alt="Развернуть" />';
$this->LANG['SpoilerHide'] = '<img src="./templates/'.DEF_SKIN.'/im/down.gif" alt="Свернуть" />';

$this->LANG['SpoilerShow'] = 'Отобразить';
$this->LANG['SpoilerHide'] = 'Скрыть';

$this->LANG['SpoilerShow'] = '<img src="./templates/'.DEF_SKIN.'/im/up.gif" />';
$this->LANG['SpoilerHide'] = '<img src="./templates/'.DEF_SKIN.'/im/down.gif" />';