Update twig_extension.rst

templating/twig_extension.rst

@@ -62,9 +62,32 @@ As an example you'll create a price filter to format a given number into price::
     versions before 1.26, include this method which is omitted in the example
     above.
 
+Here's how to create a custom **function**::
+
+    // src/AppBundle/Twig/AppExtension.php
+    namespace AppBundle\Twig;
+
+    use Twig\Extension\AbstractExtension;
+    use Twig\TwigFunction;
+
+    class AppExtension extends AbstractExtension
+    {
+        public function getFunctions()
+        {
+            return array(
+                new TwigFunction('total', array($this, 'totalFunction')),
+            );
+        }
+
+        public function totalFunction(float $price, int $quantity)
+        {
+            return $price * $quantity;
+        }
+    }
+
 .. tip::
 
-    Along with custom filters, you can also add custom `functions`_ and register
+    Along with custom filters and functions, you can also register
     `global variables`_.
 
 Register an Extension as a Service