diff --git a/core/lib/Drupal/Core/Form/form.api.php b/core/lib/Drupal/Core/Form/form.api.php
index ba0e345e02..554e2710d7 100644
--- a/core/lib/Drupal/Core/Form/form.api.php
+++ b/core/lib/Drupal/Core/Form/form.api.php
@@ -15,7 +15,7 @@
  *
  * Callback for batch_set().
  *
- * @param $MULTIPLE_PARAMS
+ * @param $multiple_params
  *   Additional parameters specific to the batch. These are specified in the
  *   array passed to batch_set().
  * @param array|\ArrayAccess $context
@@ -54,7 +54,7 @@
  *   It is discouraged to typehint this parameter as an array, to allow an
  *   object implement \ArrayAccess to be passed.
  */
-function callback_batch_operation($MULTIPLE_PARAMS, &$context) {
+function callback_batch_operation($multiple_params, &$context) {
   $node_storage = \Drupal::entityTypeManager()->getStorage('node');
   $database = \Drupal::database();
 
diff --git a/core/modules/migrate_drupal/src/Plugin/migrate/FieldMigration.php b/core/modules/migrate_drupal/src/Plugin/migrate/FieldMigration.php
index c7aaa2df35..9222e57c34 100644
--- a/core/modules/migrate_drupal/src/Plugin/migrate/FieldMigration.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/FieldMigration.php
@@ -141,24 +141,24 @@ public function getProcess() {
 
         try {
           $plugin_id = $this->cckPluginManager->getPluginIdFromFieldType($field_type, [], $this);
-          $Manager = $this->cckPluginManager;
+          $manager = $this->cckPluginManager;
         }
         catch (PluginNotFoundException $ex) {
           try {
             $plugin_id = $this->fieldPluginManager->getPluginIdFromFieldType($field_type, [], $this);
-            $Manager = $this->fieldPluginManager;
+            $manager = $this->fieldPluginManager;
           }
           catch (PluginNotFoundException $ex) {
             continue;
           }
         }
 
-        if (!isset($this->processedFieldTypes[$field_type]) && $Manager->hasDefinition($plugin_id)) {
+        if (!isset($this->processedFieldTypes[$field_type]) && $manager->hasDefinition($plugin_id)) {
           $this->processedFieldTypes[$field_type] = TRUE;
           // Allow the field plugin to alter the migration as necessary so that
           // it knows how to handle fields of this type.
           if (!isset($this->fieldPluginCache[$field_type])) {
-            $this->fieldPluginCache[$field_type] = $Manager->createInstance($plugin_id, [], $this);
+            $this->fieldPluginCache[$field_type] = $manager->createInstance($plugin_id, [], $this);
           }
         }
         $method = $this->pluginDefinition[static::PLUGIN_METHOD];
diff --git a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
index 7e4f9125b2..bb9da9411a 100644
--- a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
+++ b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
@@ -87,7 +87,7 @@ public function testUserAgentValidation() {
     $this->drupalLogout();
 
     $system_path = $base_url . '/' . drupal_get_path('module', 'system');
-    $HTTP_path = $system_path . '/tests/http.php/user/login';
+    $http_path = $system_path . '/tests/http.php/user/login';
     $https_path = $system_path . '/tests/https.php/user/login';
     // Generate a valid simpletest User-Agent to pass validation.
     $this->assertTrue(preg_match('/test\d+/', $this->databasePrefix, $matches), 'Database prefix contains test prefix.');
@@ -95,14 +95,14 @@ public function testUserAgentValidation() {
     $this->additionalCurlOptions = [CURLOPT_USERAGENT => $test_ua];
 
     // Test pages only available for testing.
-    $this->drupalGet($HTTP_path);
+    $this->drupalGet($http_path);
     $this->assertResponse(200, 'Requesting http.php with a legitimate simpletest User-Agent returns OK.');
     $this->drupalGet($https_path);
     $this->assertResponse(200, 'Requesting https.php with a legitimate simpletest User-Agent returns OK.');
 
     // Now slightly modify the HMAC on the header, which should not validate.
     $this->additionalCurlOptions = [CURLOPT_USERAGENT => $test_ua . 'X'];
-    $this->drupalGet($HTTP_path);
+    $this->drupalGet($http_path);
     $this->assertResponse(403, 'Requesting http.php with a bad simpletest User-Agent fails.');
     $this->drupalGet($https_path);
     $this->assertResponse(403, 'Requesting https.php with a bad simpletest User-Agent fails.');
@@ -110,7 +110,7 @@ public function testUserAgentValidation() {
     // Use a real User-Agent and verify that the special files http.php and
     // https.php can't be accessed.
     $this->additionalCurlOptions = [CURLOPT_USERAGENT => 'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12'];
-    $this->drupalGet($HTTP_path);
+    $this->drupalGet($http_path);
     $this->assertResponse(403, 'Requesting http.php with a normal User-Agent fails.');
     $this->drupalGet($https_path);
     $this->assertResponse(403, 'Requesting https.php with a normal User-Agent fails.');
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index a593e62c7d..3863fb798e 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -77,6 +77,10 @@
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/InfoFiles/ClassFilesSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/InfoFiles/DuplicateEntrySniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/InfoFiles/RequiredSniff.php"/>
+  <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/NamingConventions/ValidVariableNameSniff.php">
+    <!-- Sniff for: LowerStart -->
+    <exclude name="Drupal.NamingConventions.ValidVariableName.LowerCamelName"/>
+  </rule>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Scope/MethodScopeSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Semantics/EmptyInstallSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Semantics/FunctionTSniff.php">