diff --git a/README.md b/README.md
index c6c22971b1c14f2a2eb37c2fa6c88ab1c7fc4899..7494ae939d5155f80ab45f1ef36f512f7b34d605 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,14 @@
-Provides a widget for inline management (creation, modification, removal) of referenced entities.
-The primary use case is the parent -> children one (product display -> products, order -> line items, etc.),
+Provides a widget for inline management (creation, modification, removal) of
+referenced entities.
+The primary use case is the parent -> children one (product display -> products,
+order -> line items, etc.),
 where the child entities are never managed outside the parent form.
 Existing entities can also be referenced.
 
-Supports commerce_product_reference, commerce_line_item_reference and entityreference fields.
-Requires integration code to be provided for each entity type that can be referenced.
+Supports commerce_product_reference, commerce_line_item_reference and
+entityreference fields.
+Requires integration code to be provided for each entity type that can be
+referenced.
 Supports the commerce_product (including Commerce AutoSKU integraton),
 commerce_line_item, node, taxonomy_term entity types out of the box.
 
diff --git a/inline_entity_form.api.php b/inline_entity_form.api.php
index 3a9fcdc7717ad92e306c5555f66105f2821a6e55..c0a58d77140cc47315c34a555f9da261c0404357 100644
--- a/inline_entity_form.api.php
+++ b/inline_entity_form.api.php
@@ -10,10 +10,10 @@
  *
  * @param array $entity_form
  *   Nested array of form elements that comprise the entity form.
- * @param $form_state
+ * @param FormStateInterface $form_state
  *   The form state of the parent form.
  */
-function hook_inline_entity_form_entity_form_alter(array &$entity_form, \Drupal\Core\Form\FormStateInterface &$form_state) {
+function hook_inline_entity_form_entity_form_alter(array &$entity_form, FormStateInterface &$form_state) {
   if ($entity_form['#entity_type'] == 'commerce_line_item') {
     $entity_form['quantity']['#description'] = t('New quantity description.');
   }
@@ -27,10 +27,10 @@ function hook_inline_entity_form_entity_form_alter(array &$entity_form, \Drupal\
  *
  * @param array $reference_form
  *   Nested array of form elements that comprise the reference form.
- * @param $form_state
+ * @param FormStateInterface $form_state
  *   The form state of the parent form.
  */
-function hook_inline_entity_form_reference_form_alter(array &$reference_form, \Drupal\Core\Form\FormStateInterface &$form_state) {
+function hook_inline_entity_form_reference_form_alter(array &$reference_form, FormStateInterface &$form_state) {
   $reference_form['entity_id']['#description'] = t('New autocomplete description');
 }
 
diff --git a/inline_entity_form.module b/inline_entity_form.module
index fcb428bd9d1a8d35d5d38857de5e72679f26c8a5..2b1e631b47f83b7371321991d70b65f10fae8ffe 100644
--- a/inline_entity_form.module
+++ b/inline_entity_form.module
@@ -503,12 +503,12 @@ function inline_entity_form_migration_plugins_alter(array &$migrations) {
 /**
  * Change text button by type of bundle.
  *
- * @param $form
+ * @param array $form
  *   The complete parent form.
- * @param $form_state
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
  *   The form state of the parent form.
  */
-function inline_entity_form_change_bundle_form($form, FormStateInterface $form_state) {
+function inline_entity_form_change_bundle_form(array $form, FormStateInterface $form_state) {
   $element = inline_entity_form_get_element($form, $form_state);
   $elements = $form_state->getTriggeringElement();
 
diff --git a/src/Element/InlineEntityForm.php b/src/Element/InlineEntityForm.php
index 609a6b910596f593372663cd49c6742b135b82c7..933ad327f22f9fbc5bc9d13d6a436f3c9894c813 100644
--- a/src/Element/InlineEntityForm.php
+++ b/src/Element/InlineEntityForm.php
@@ -177,8 +177,9 @@ class InlineEntityForm extends RenderElement {
    *   The entity form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
-   * 
-   * @return Drupal\Core\Entity\EntityInterface\null
+   *
+   * @return Drupal\Core\Entity\EntityInterface|null
+   *   Returns saved entity if true, else null.
    */
   public static function submitEntityForm(array &$entity_form, FormStateInterface $form_state) {
     $inline_form_handler = static::getInlineFormHandler($entity_form['#entity_type']);
diff --git a/src/Form/ConfigEntityInlineForm.php b/src/Form/ConfigEntityInlineForm.php
index fef46993a0db2b0bf6499424b14e40de1fd9e1cd..afa63cef14fae597740876b07371560e32edfddb 100644
--- a/src/Form/ConfigEntityInlineForm.php
+++ b/src/Form/ConfigEntityInlineForm.php
@@ -64,7 +64,7 @@ class ConfigEntityInlineForm extends EntityInlineForm {
       $form_object = $this->getFormObject($entity, $entity_form['#form_mode']);
       $form_object->validateForm($entity_form, $this->getSubformState($entity_form, $form_state));
 
-      foreach ($form_state->getErrors() as $name => $message) {
+      foreach ($form_state->getErrors() as $message) {
         // $name may be unknown in $form_state and
         // $form_state->setErrorByName($name, $message) may suppress the error
         // message.
diff --git a/src/Form/NodeInlineForm.php b/src/Form/NodeInlineForm.php
index ac94656d43f1b7d5ff357bf5e2d7bfdc68f0d38c..85a263114393ca6c76667f75ece5760d6948973b 100644
--- a/src/Form/NodeInlineForm.php
+++ b/src/Form/NodeInlineForm.php
@@ -3,8 +3,6 @@
 namespace Drupal\inline_entity_form\Form;
 
 use Drupal\Core\StringTranslation\StringTranslationTrait;
-use Drupal\Core\Form\FormStateInterface;
-use Drupal\Core\Entity\EntityInterface;
 
 /**
  * Node inline form handler.
diff --git a/src/MigrationHelper.php b/src/MigrationHelper.php
index e4646023dc60e74376f5964c58d77998e91381f5..841177bc4d5f6503ede6059489582ec50876c120 100644
--- a/src/MigrationHelper.php
+++ b/src/MigrationHelper.php
@@ -165,8 +165,8 @@ class MigrationHelper {
             $merged_values = array_replace_recursive($group_value, $migration_value);
             $migration[$key] = $merged_values;
           }
-          // Where the group provides a value the migration doesn't, use the group
-          // value.
+          // Where the group provides a value the migration doesn't,
+          // use the group value.
           elseif (is_null($migration_value)) {
             $migration[$key] = $group_value;
           }
diff --git a/src/Plugin/Field/FieldWidget/InlineEntityFormBase.php b/src/Plugin/Field/FieldWidget/InlineEntityFormBase.php
index 17c6cae129897598ce11dcee29db88df134bc990..19ae6e7d67b2dc57e752b857423e4d173d3fb1b4 100644
--- a/src/Plugin/Field/FieldWidget/InlineEntityFormBase.php
+++ b/src/Plugin/Field/FieldWidget/InlineEntityFormBase.php
@@ -277,7 +277,7 @@ abstract class InlineEntityFormBase extends WidgetBase implements ContainerFacto
       $labels = $this->getSetting('labels');
       $element['labels']['label_singular_' . $bundle] = [
         '#type' => 'textfield',
-        '#title' => $this->t('Singular label ' . $bundle),
+        '#title' => $this->t('Singular label @bundle', ['@bundle' => $bundle]),
         '#default_value' => ($labels ? $labels['label_singular_' . $bundle] : NULL),
         '#states' => [
           'visible' => [
@@ -287,7 +287,7 @@ abstract class InlineEntityFormBase extends WidgetBase implements ContainerFacto
       ];
       $element['labels']['label_plural_' . $bundle] = [
         '#type' => 'textfield',
-        '#title' => $this->t('Plural label ' . $bundle),
+        '#title' => $this->t('Plural label @bundle', ['@bundle' => $bundle]),
         '#default_value' => ($labels ? $labels['label_plural_' . $bundle] : NULL),
         '#states' => [
           'visible' => [
@@ -304,7 +304,7 @@ abstract class InlineEntityFormBase extends WidgetBase implements ContainerFacto
         'visible' => [
           ':input[name="' . $states_prefix . '[override_labels]"]' => ['checked' => TRUE],
           'and',
-          ':input[name="' . $states_prefix . '[config_labels_button]"]' => ['!value' => 'complex_label'],
+          ':input[name="' . $states_prefix . '[config_labels_button]"]' => [['!value' => 'complex_label']],
         ],
       ],
     ];
@@ -479,7 +479,7 @@ abstract class InlineEntityFormBase extends WidgetBase implements ContainerFacto
   }
 
   /**
-   *
+   * Checks if the entity is opened from the query parameter in the form state.
    */
   public static function entityIsOpenFromQuery(ContentEntityInterface $entity, FormStateInterface $form_state) {
     $query = \Drupal::request()->query;
diff --git a/src/Plugin/Field/FieldWidget/InlineEntityFormComplex.php b/src/Plugin/Field/FieldWidget/InlineEntityFormComplex.php
index 20885e8b97d78b87d6a66e56ec127bf9f870902d..fb9e1fdad63de5cff45cac6a48330bb8d8266876 100644
--- a/src/Plugin/Field/FieldWidget/InlineEntityFormComplex.php
+++ b/src/Plugin/Field/FieldWidget/InlineEntityFormComplex.php
@@ -1263,7 +1263,10 @@ class InlineEntityFormComplex extends InlineEntityFormBase implements ContainerF
   }
 
   /**
+   * Retrieves the labels for the entity type.
+   *
    * @return array|\Drupal\Core\Entity\EntityTypeInterface
+   *   An array with entity type labels or labels from parent class.
    */
   protected function getEntityTypeLabels() {
     if ($this->getSetting('override_labels')) {
@@ -1282,6 +1285,7 @@ class InlineEntityFormComplex extends InlineEntityFormBase implements ContainerF
    * Generate unique wrapper id for IEF element.
    *
    * @param string $ief_id
+   *   The ID of the IEF element.
    */
   public static function getWrapperId($ief_id) {
     static $ids = [];
diff --git a/src/Tests/ContentModerationTranslationTest.php b/src/Tests/ContentModerationTranslationTest.php
index d2e8a2008238bf701834f2a354e0543b1f974cb7..37622273bf7d355d7d32054dd17d9baa6de903ec 100644
--- a/src/Tests/ContentModerationTranslationTest.php
+++ b/src/Tests/ContentModerationTranslationTest.php
@@ -58,7 +58,7 @@ class ContentModerationTranslationTest extends InlineEntityFormTestBase {
       $edit['settings[node][' . $node_type . '][translatable]'] = TRUE;
       $edit['settings[node][' . $node_type . '][settings][language][language_alterable]'] = TRUE;
     }
-    $this->submitForm('admin/config/regional/content-language', $edit, t('Save configuration'));
+    $this->submitForm('admin/config/regional/content-language', $edit, $this->t('Save configuration'));
 
     // Allow referencing existing entities.
     $form_display_storage = $this->container->get('entity_type.manager')->getStorage('entity_form_display');
@@ -111,7 +111,7 @@ class ContentModerationTranslationTest extends InlineEntityFormTestBase {
       'title[0][value]' => 'A node',
       'langcode[0][value]' => 'en',
     ];
-    $this->submitForm(NULL, $edit, t('Save'));
+    $this->submitForm(NULL, $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200, 'Saving the parent entity was successful.');
 
     // Both inline nodes should now be in English.
@@ -126,7 +126,7 @@ class ContentModerationTranslationTest extends InlineEntityFormTestBase {
     $edit = [
       'langcode[0][value]' => 'de',
     ];
-    $this->submitForm(NULL, $edit, t('Save'));
+    $this->submitForm(NULL, $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200, 'Saving the parent entity was successful.');
 
     // Both inline nodes should now be in German.
@@ -166,7 +166,7 @@ class ContentModerationTranslationTest extends InlineEntityFormTestBase {
     ];
     $this->submitForm(NULL, $edit, $this->getButtonName('//input[@type="submit" and @value="Update node" and @data-drupal-selector="edit-multi-form-inline-entity-form-entities-1-form-actions-ief-edit-save"]'));
 
-    $this->submitForm(NULL, [], t('Save (this translation)'));
+    $this->submitForm(NULL, [], $this->t('Save (this translation)'));
     $this->assertSession()->statusCodeEquals(200, 'Saving the parent entity was successful.');
 
     // Load using the original titles, confirming they haven't changed.
diff --git a/src/WidgetSubmit.php b/src/WidgetSubmit.php
index a6fec3fa61cad8ec8a964d4f580a2075072d780f..905d500a89de5d085aceb4e4ff78759deedab9b3 100644
--- a/src/WidgetSubmit.php
+++ b/src/WidgetSubmit.php
@@ -58,13 +58,14 @@ class WidgetSubmit {
           $handler->save($entity);
           $referenceUpgrader->registerEntity($entity);
           $entity_item['needs_save'] = FALSE;
-          \Drupal::moduleHandler()->invokeAll('inline_entity_form_entity_save', [&$form_state, $entity, $is_new]);
+          \Drupal::moduleHandler()->invokeAll('inline_entity_form_entity_save',
+          [&$form_state, $entity, $is_new]);
         }
       }
 
       /** @var \Drupal\Core\Entity\ContentEntityInterface $entities */
       foreach ($widget_state['delete'] as $entity) {
-        \Drupal::moduleHandler()->invokeAll('inline_entity_form_entity_delete', [&$form_state, $entity]);
+        \Drupal::moduleHandler()->invokeAll('inline_entity_form_entity_delete',[&$form_state, $entity]);
         $entity->delete();
       }
       unset($widget_state['delete']);
diff --git a/tests/modules/inline_entity_form_test/inline_entity_form_test.module b/tests/modules/inline_entity_form_test/inline_entity_form_test.module
index 260d456daea2d1d3277f1fe59cc6f0c7e15b76a1..5c8df8f9206f97824236e9e1e6ee0ab4f98dbb0b 100644
--- a/tests/modules/inline_entity_form_test/inline_entity_form_test.module
+++ b/tests/modules/inline_entity_form_test/inline_entity_form_test.module
@@ -10,7 +10,7 @@ use Drupal\Core\Ajax\HtmlCommand;
 use Drupal\Core\Form\FormStateInterface;
 
 /**
- * Implements hook_form_BASE_FORM_ID_alter for node_ief_simple_single_form.
+ * Implements hook_form_BASE_FORM_ID_alter() for node_ief_simple_single_form.
  *
  * Adds an element and a button to update the element via AJAX.
  */