添加Twig Extension类会导致编译错误

我正在使用Silex(1.3)为一个项目，我想添加一个Twig扩展，符合Twig_Extension接口:

namespace LizardCMS'Twig'Extension;
class DateExtension extends Twig_Extension {
public function getFilters() {
    array(new 'Twig_SimpleFilter($this, 'relative'));
}
public function relative($date) {
    $date = new 'DateTime($date);
    $difference = time() - $date->getTimestamp();
    $periods = array("seconde", "minute", "heure", "jour", "semaine", "mois", "an", "decade");
    $lengths = array("60", "60", "24", "7", "4.35", "12", "10");
    for ($j = 0; $difference >= $lengths[$j] and $j < 7; $j++)
        $difference /= $lengths[$j];
        $difference = round($difference);
        if ($difference != 1) {
            $periods[$j].= "s";
    }
    $text = "il y $difference $periods[$j]";
    return $text;
}
public function timestamp($date) {
    $datetime = new 'DateTime($date);
    return "il y a ".$datetime->getTimestamp()." secondes";
}
public function daymonthyear($date, $withSlashes = true) {
    $datetime = new 'DateTime($date);
    $separator = ($withSlashes ? "/" : "-");
    return "le ".$datetime->format("d".$separator."m".$separator."Y");
}
public function chosenDateTimeFormat($app, $date) {
    $format = strtolower($app['controller.configuration']->findAll()->getDateTimeFormat()); 
    if(in_array($format, array("relative", "timestamp", "daymonthyear"))) {
        return $this->$format($date);
    } 
}
public function getName() {
    return 'Date';    
}
}

添加后:

  $app["twig"] = $app->share($app->extend("twig", function ('Twig_Environment $twig, Silex'Application $app) {
$twig->addExtension(new LizardCMS'Twig'Extension'DateExtension());
return $twig;
}));

…这个可爱的错误出现了:

Twig_Error_Syntax in Environment.php line 601: An exception has been thrown during the compilation of a template ("Warning: Invalid argument supplied for foreach()") in "index.html.twig".

但是在我的foreach中没有问题，因为如果我删除我的Twig扩展，模板加载没有任何错误。

在bootstrap文件中添加过滤器和函数对我来说真的很烦人。

任何帮助将不胜感激!