Fix "Back Button Works Only on First Form When Multiple Forms Exist"

src/EventListener/CompileFormFieldsListener.php

@@ -77,8 +77,9 @@ public function __invoke(array $formFields, string $formId, Form $form): array
             $manager->storeStepData($stepData);
         }
 
-        // Redirect back if asked for it
-        if ('back' === $request->request->get('mp_form_pageswitch')) {
+        // Redirect back if asked for it, using the per-form page switch name so
+        // forms on the same page don't interfere with each other.
+        if ('back' === $request->request->get($manager->getPageSwitchFormFieldName())) {
             $manager->redirectToStep($manager->getPreviousStep());
         }
 

src/EventListener/PrepareFomDataListener.php

@@ -39,7 +39,9 @@ public function __invoke(array &$submitted, array &$labels, array $fields, Form
         $submittedBag = new ParameterBag($submitted);
         $labelsBag = new ParameterBag($labels);
 
-        $pageSwitchValue = $submittedBag->get('mp_form_pageswitch', '');
+        // Use the per-form page switch name so multiple forms on the same page don't interfere.
+        $pageSwitchKey = $manager->getPageSwitchFormFieldName();
+        $pageSwitchValue = $submittedBag->get($pageSwitchKey, '');
 
         // Store data in session
         $stepData = $manager->getDataOfCurrentStep();
@@ -64,7 +66,7 @@ public function __invoke(array &$submitted, array &$labels, array $fields, Form
             // need it because otherwise it's not possible to have an empty step (e.g. only
             // explanation fields) as the step data would be empty and getFirstInvalidStep()
             // would return the one before the empty step.
-            unset($submitted['mp_form_pageswitch']);
+            unset($submitted[$pageSwitchKey]);
 
             // Add session data for Contao 4.13
             if (version_compare(ContaoCoreBundle::getVersion(), '5.0', '<')) {

src/FormManager.php

@@ -347,6 +347,16 @@ private function isPageBreak(FormFieldModel $formField): bool
         return 'mp_form_pageswitch' === $formField->type;
     }
 
+    /**
+     * Returns the form field name used for the page switch control for this form.
+     */
+    public function getPageSwitchFormFieldName(): string
+    {
+        $this->prepare();
+
+        return 'mp_form_pageswitch_'.$this->formModel->id;
+    }
+
     private function loadFormFieldModels(): void
     {
         $collection = $this->contaoFramework->getAdapter(FormFieldModel::class)->findPublishedByPid($this->formModel->id);
@@ -422,8 +432,11 @@ private function prepare(): void
             if ($this->isPageBreak($formField)) {
                 $isPageBreakLastFormField = true;
 
-                // Set the name on the model, otherwise one has to enter it in the back end every time
-                $formField->name = $formField->type;
+                // Set a unique name on the model (per form) to allow multiple forms on the
+                // same page to work independently. Previously this was always
+                // "mp_form_pageswitch" which caused collisions when multiple forms were
+                // present.
+                $formField->name = $formField->type.'_'.$this->formModel->id;
 
                 // Increase counter
                 ++$i;

src/Widget/Placeholder.php

@@ -143,7 +143,7 @@ private function generateTokens(): array
             }
 
             // Also skip Contao internal tokens and the page switch element
-            if (\in_array($k, ['REQUEST_TOKEN', 'FORM_SUBMIT', 'mp_form_pageswitch'], true)) {
+            if (\in_array($k, ['REQUEST_TOKEN', 'FORM_SUBMIT', $manager->getPageSwitchFormFieldName()], true)) {
                 continue;
             }
 

tests/EventListener/PrepareFormDataListenerTest.php

@@ -36,7 +36,7 @@ public function testDataIsStoredProperlyAndDoesNotAdjustHookParametersIfNotOnLas
 
         $listener = new PrepareFomDataListener($factory, $this->createMock(RequestStack::class), $this->createMock(FileUploadNormalizer::class));
 
-        $submitted = ['submitted2' => 'foobar', 'mp_form_pageswitch' => 'continue'];
+        $submitted = ['submitted2' => 'foobar', 'mp_form_pageswitch_42' => 'continue'];
         $labels = [];
         $fields = [];
         $files = [];
@@ -45,27 +45,27 @@ public function testDataIsStoredProperlyAndDoesNotAdjustHookParametersIfNotOnLas
             $listener($submitted, $labels, $fields, $form, $files);
         } catch (RedirectResponseException $exception) {
             $this->assertSame(
-                'https://www.example.com/form?step=2&ref='.self::SESSION_IDENTIFIER,
+                'https://www.example.com/form?step=2&ref=' . self::SESSION_IDENTIFIER,
                 $exception->getResponse()->headers->get('Location'),
             );
         }
 
-        $this->assertSame(['submitted2' => 'foobar', 'mp_form_pageswitch' => 'continue'], $submitted); // "mp_form_pageswitch" should not be removed
+        $this->assertSame(['submitted2' => 'foobar', 'mp_form_pageswitch_42' => 'continue'], $submitted); // pageswitch should not be removed
         $this->assertSame([], $labels); // Test we do not modify the hook parameters if not in last step
 
         $manager = $factory->forFormId(42);
 
-        $this->assertSame(['submitted1' => 'foobar', 'submitted2' => 'foobar', 'mp_form_pageswitch' => 'continue'], $manager->getDataOfAllSteps()->getAllSubmitted());
+        $this->assertSame(['submitted1' => 'foobar', 'submitted2' => 'foobar', 'mp_form_pageswitch_42' => 'continue'], $manager->getDataOfAllSteps()->getAllSubmitted());
         $this->assertSame(['label1' => 'foobar'], $manager->getDataOfAllSteps()->getAllLabels());
     }
 
     public function testDataIsStoredProperlyAndDoesAdjustHookParametersOnLastStep(): void
     {
         $stepData = StepData::create(0);
-        $stepData = $stepData->withSubmitted(new ParameterBag(['submitted1' => 'foobar', 'mp_form_pageswitch' => 'continue']));
+        $stepData = $stepData->withSubmitted(new ParameterBag(['submitted1' => 'foobar', 'mp_form_pageswitch_42' => 'continue']));
         $stepData = $stepData->withLabels(new ParameterBag(['label1' => 'foobar']));
         $stepData2 = StepData::create(1);
-        $stepData2 = $stepData2->withSubmitted(new ParameterBag(['submitted2' => 'foobar', 'mp_form_pageswitch' => 'continue']));
+        $stepData2 = $stepData2->withSubmitted(new ParameterBag(['submitted2' => 'foobar', 'mp_form_pageswitch_42' => 'continue']));
         $initialData = (new StepDataCollection())->set($stepData)->set($stepData2);
         $storage = $this->createStorage($initialData);
 
@@ -80,7 +80,7 @@ public function testDataIsStoredProperlyAndDoesAdjustHookParametersOnLastStep():
 
         $listener = new PrepareFomDataListener($factory, $this->createMock(RequestStack::class), $this->createMock(FileUploadNormalizer::class));
 
-        $submitted = ['submitted3' => 'foobar', 'mp_form_pageswitch' => 'continue'];
+        $submitted = ['submitted3' => 'foobar', 'mp_form_pageswitch_42' => 'continue'];
         $labels = [];
         $fields = [];
         $files = [];