class SomeExtension extends Twig_Extension
 {
     public function getFunctions()
     {
         return [
-            'is_mobile' => new Twig_Function_Method($this, 'isMobile'),
+             new Twig_SimpleFunction('is_mobile', [$this, 'isMobile']),
         ];
     }

     public function getFilters()
     {
         return [
-            'is_mobile' => new Twig_Filter_Method($this, 'isMobile'),
+             new Twig_SimpleFilter('is_mobile', [$this, 'isMobile']),
         ];
     }
 }