diff --git a/reference/forms/types/choice.rst b/reference/forms/types/choice.rst
index a2790af5c0d..dc6fa188a28 100644
--- a/reference/forms/types/choice.rst
+++ b/reference/forms/types/choice.rst
@@ -92,19 +92,18 @@ method::
             new Category('Cat3'),
             new Category('Cat4'),
         ],
-        'choice_label' => function($category, $key, $index) {
+        'choice_label' => function($category, $index, $key) {
             /** @var Category $category */
             return strtoupper($category->getName());
         },
-        'choice_attr' => function($category, $key, $index) {
+        'choice_attr' => function($category, $index, $key) {
             return ['class' => 'category_'.strtolower($category->getName())];
         },
-        
-        'group_by' => function($category, $key, $index) {
+        'group_by' => function($category, $index, $key) {
             // randomly assign things into 2 groups
             return rand(0, 1) == 1 ? 'Group A' : 'Group B';
         },
-        'preferred_choices' => function($category, $key, $index) {
+        'preferred_choices' => function($category, $index, $key) {
             return $category->getName() == 'Cat2' || $category->getName() == 'Cat3';
         },
     ]);
diff --git a/reference/forms/types/options/choice_attr.rst.inc b/reference/forms/types/options/choice_attr.rst.inc
index 9b74a6b13e7..a70e67e6d9a 100644
--- a/reference/forms/types/options/choice_attr.rst.inc
+++ b/reference/forms/types/options/choice_attr.rst.inc
@@ -18,7 +18,7 @@ If an array, the keys of the ``choices`` array must be used as keys::
             'No' => false,
             'Maybe' => null,
         ),
-        'choice_attr' => function($val, $key, $index) {
+        'choice_attr' => function($val, $index, $key) {
             // adds a class like attending_yes, attending_no, etc
             return ['class' => 'attending_'.strtolower($key)];
         },
diff --git a/reference/forms/types/options/choice_label.rst.inc b/reference/forms/types/options/choice_label.rst.inc
index 0dbf1f1e89d..c09710f45d2 100644
--- a/reference/forms/types/options/choice_label.rst.inc
+++ b/reference/forms/types/options/choice_label.rst.inc
@@ -16,7 +16,7 @@ more control::
             'no' => false,
             'maybe' => null,
         ),
-        'choice_label' => function ($value, $key, $index) {
+        'choice_label' => function ($value, $index, $key) {
             if ($value == true) {
                 return 'Definitely!';
             }
diff --git a/reference/forms/types/options/group_by.rst.inc b/reference/forms/types/options/group_by.rst.inc
index 31ded648baa..be62a8d5084 100644
--- a/reference/forms/types/options/group_by.rst.inc
+++ b/reference/forms/types/options/group_by.rst.inc
@@ -22,7 +22,7 @@ Take the following example::
             '1 week' => new \DateTime('+1 week'),
             '1 month' => new \DateTime('+1 month')
         ),
-        'group_by' => function($val, $key, $index) {
+        'group_by' => function($val, $index, $key) {
             if ($val <= new \DateTime('+3 days')) {
                 return 'Soon';
             } else {