Clarify $formId parameter (#1636)

Author: fritzmg

docs/dev/reference/hooks/compileFormFields.md

@@ -21,8 +21,7 @@ and expects the modified form fields as return value.
 
 2. *string* `$formId`
 
-	  Alias of the current form. Used in the `value` attribute of the hidden form
-    field `FORM_SUBMIT`. Don't confuse with `$objForm->id`.
+	Alias of the current form with the prefix `auto_`. Don't confuse with `$form->id`.
 
 3. *\Contao\Form* `$form`
 

docs/dev/reference/hooks/loadFormField.md

@@ -22,8 +22,7 @@ field of the form generator.
 
 2. *string* `$formId`
 
-    Alias of the current form. Used in the `value` attribute of the hidden form
-    field `FORM_SUBMIT`. Don't confuse with `$form->id`.
+    Alias of the current form with the prefix `auto_`. Don't confuse with `$form->id`.
 
 3. *array* `$formData`
 
@@ -55,7 +54,7 @@ class LoadFormFieldListener
 {
     public function __invoke(Widget $widget, string $formId, array $formData, Form $form): Widget
     {
-        if ('myForm' === $formId) {
+        if ('myForm' === $form->formID) {
             $widget->class.= ' myclass';
         }
 

docs/dev/reference/hooks/validateFormField.md

@@ -21,7 +21,7 @@ object as return value.
 
 2. *string* `$formId`
 
-    Alias of the current form. Used in the `value` attribute of the hidden form field `FORM_SUBMIT`. Do not confuse with `$form->id`.
+    Alias of the current form with the prefix `auto_`. Don't confuse with `$form->id`.
 
 3. *array* `$formData`
 
@@ -52,7 +52,7 @@ class ValidateFormFieldListener
 {
     public function __invoke(Widget $widget, string $formId, array $formData, Form $form): Widget
     {
-        if ('myform' === $formId && 'mywidget' === $widget->name) {
+        if ('myform' === $form->formID && 'mywidget' === $widget->name) {
             // Do your custom validation and add an error if widget does not validate
             // …