diff --git a/lib/AdminPages/Pages/Newsletters.php b/lib/AdminPages/Pages/Newsletters.php
index 371b591021..b78ca74f30 100644
--- a/lib/AdminPages/Pages/Newsletters.php
+++ b/lib/AdminPages/Pages/Newsletters.php
@@ -73,7 +73,7 @@ class Newsletters {
   }
 
   public function render() {
-    global $wpRoles;
+    global $wp_roles; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
 
     $data = [];
 
@@ -90,7 +90,7 @@ class Newsletters {
     $data['current_wp_user'] = $this->wp->wpGetCurrentUser()->to_array();
     $data['current_wp_user_firstname'] = $this->wp->wpGetCurrentUser()->user_firstname;
     $data['site_url'] = $this->wp->siteUrl();
-    $data['roles'] = $wpRoles->get_names();
+    $data['roles'] = $wp_roles->get_names(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $data['roles']['mailpoet_all'] = $this->wp->__('In any WordPress role', 'mailpoet');
 
     $installedAtDateTime = new \DateTime($data['settings']['installed_at']);
diff --git a/lib/AdminPages/Pages/Update.php b/lib/AdminPages/Pages/Update.php
index 081cff70a0..6a236d5f7a 100644
--- a/lib/AdminPages/Pages/Update.php
+++ b/lib/AdminPages/Pages/Update.php
@@ -28,7 +28,7 @@ class Update {
 
   public function render() {
     global $wp;
-    $currentUrl = $this->wp->homeUrl(add_query_arg($wp->queryString, $wp->request));
+    $currentUrl = $this->wp->homeUrl(add_query_arg($wp->query_string, $wp->request)); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $redirectUrl =
       (!empty($_GET['mailpoet_redirect']))
         ? urldecode($_GET['mailpoet_redirect'])
diff --git a/lib/Analytics/Reporter.php b/lib/Analytics/Reporter.php
index e9f015687c..de006a36c6 100644
--- a/lib/Analytics/Reporter.php
+++ b/lib/Analytics/Reporter.php
@@ -27,7 +27,7 @@ class Reporter {
   }
 
   public function getData() {
-    global $wpdb, $wpVersion, $woocommerce;
+    global $wpdb, $wp_version, $woocommerce;  // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $mta = $this->settings->get('mta', []);
     $newsletters = Newsletter::getAnalytics();
     $isCronTriggerMethodWP = $this->settings->get('cron_trigger.method') === CronTrigger::METHOD_WORDPRESS;
@@ -41,7 +41,7 @@ class Reporter {
     $result = [
       'PHP version' => PHP_VERSION,
       'MySQL version' => $wpdb->db_version(),
-      'WordPress version' => $wpVersion,
+      'WordPress version' => $wp_version, // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       'Multisite environment' => WPFunctions::get()->isMultisite() ? 'yes' : 'no',
       'RTL' => WPFunctions::get()->isRtl() ? 'yes' : 'no',
       'WP_MEMORY_LIMIT' => WP_MEMORY_LIMIT,
diff --git a/lib/AutomaticEmails/AutomaticEmails.php b/lib/AutomaticEmails/AutomaticEmails.php
index dced949145..d450c0012f 100644
--- a/lib/AutomaticEmails/AutomaticEmails.php
+++ b/lib/AutomaticEmails/AutomaticEmails.php
@@ -45,9 +45,10 @@ class AutomaticEmails {
   }
 
   public function getAutomaticEmails() {
-    global $wpFilter;
+    global $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
 
-    $registeredGroups = preg_grep('!^' . self::FILTER_PREFIX . '(.*?)$!', array_keys($wpFilter));
+    // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $registeredGroups = preg_grep('!^' . self::FILTER_PREFIX . '(.*?)$!', array_keys($wp_filter));
 
     if (empty($registeredGroups)) return null;
 
@@ -126,9 +127,10 @@ class AutomaticEmails {
   }
 
   public function unregisterAutomaticEmails() {
-    global $wpFilter;
+    global $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
 
-    $registeredGroups = preg_grep('!^' . self::FILTER_PREFIX . '(.*?)$!', array_keys($wpFilter));
+    // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $registeredGroups = preg_grep('!^' . self::FILTER_PREFIX . '(.*?)$!', array_keys($wp_filter));
 
     if (empty($registeredGroups)) return null;
 
diff --git a/lib/Cron/Workers/SendingQueue/Migration.php b/lib/Cron/Workers/SendingQueue/Migration.php
index 07c42ed72c..f0dd195b03 100644
--- a/lib/Cron/Workers/SendingQueue/Migration.php
+++ b/lib/Cron/Workers/SendingQueue/Migration.php
@@ -143,7 +143,7 @@ class Migration extends SimpleWorker {
             $queue['id']
           ));
           // link the queue with the task via task_id
-          $newTaskId = $wpdb->insertId;
+          $newTaskId = $wpdb->insert_id; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
           $wpdb->query(sprintf(
             'UPDATE %1$s SET `task_id` = %2$s WHERE `id` = %3$s',
             MP_SENDING_QUEUES_TABLE,
diff --git a/lib/DynamicSegments/Filters/WooCommerceCategory.php b/lib/DynamicSegments/Filters/WooCommerceCategory.php
index 67a00c182a..be1b799e2f 100644
--- a/lib/DynamicSegments/Filters/WooCommerceCategory.php
+++ b/lib/DynamicSegments/Filters/WooCommerceCategory.php
@@ -41,9 +41,9 @@ class WooCommerceCategory implements Filter {
       "itemmeta.order_item_id = items.order_item_id AND itemmeta.meta_key = '_product_id'",
       'itemmeta'
     );
-    $orm->join($wpdb->termRelationships, ['itemmeta.meta_value', '=', 'term_relationships.object_id'], 'term_relationships');
+    $orm->join($wpdb->term_relationships, ['itemmeta.meta_value', '=', 'term_relationships.object_id'], 'term_relationships'); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $orm->rawJoin(
-      'INNER JOIN ' . $wpdb->termTaxonomy,
+      'INNER JOIN ' . $wpdb->term_taxonomy, // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       '
          term_taxonomy.term_taxonomy_id=term_relationships.term_taxonomy_id
          AND
diff --git a/lib/Newsletter/Editor/PostTransformerContentsExtractor.php b/lib/Newsletter/Editor/PostTransformerContentsExtractor.php
index 1cda5a17c2..03bd5dce5b 100644
--- a/lib/Newsletter/Editor/PostTransformerContentsExtractor.php
+++ b/lib/Newsletter/Editor/PostTransformerContentsExtractor.php
@@ -56,12 +56,12 @@ class PostTransformerContentsExtractor {
      *
      * https://mailpoet.atlassian.net/browse/MAILPOET-1365
      */
-    global $contentWidth; // default is NULL
+    global $content_width; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps, default is NULL
 
-    $contentWidthCopy = $contentWidth;
-    $contentWidth = Env::NEWSLETTER_CONTENT_WIDTH;
+    $contentWidthCopy = $content_width; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $content_width = Env::NEWSLETTER_CONTENT_WIDTH; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $imageInfo = $this->wp->wpGetAttachmentImageSrc($id, 'mailpoet_newsletter_max');
-    $contentWidth = $contentWidthCopy;
+    $content_width = $contentWidthCopy; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
 
     return $imageInfo;
   }
diff --git a/lib/Settings/Pages.php b/lib/Settings/Pages.php
index 0c0158231d..fd2b360b33 100644
--- a/lib/Settings/Pages.php
+++ b/lib/Settings/Pages.php
@@ -83,7 +83,7 @@ class Pages {
     $subscriptionUrlFactory = Subscription\SubscriptionUrlFactory::getInstance();
     return [
       'id' => $page->ID,
-      'title' => $page->postTitle,
+      'title' => $page->post_title, // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       'url' => [
         'unsubscribe' => $subscriptionUrlFactory->getSubscriptionUrl($page, 'unsubscribe'),
         'manage' => $subscriptionUrlFactory->getSubscriptionUrl($page, 'manage'),
diff --git a/lib/Subscription/Pages.php b/lib/Subscription/Pages.php
index 2cd5892ea4..6425e866e3 100644
--- a/lib/Subscription/Pages.php
+++ b/lib/Subscription/Pages.php
@@ -178,7 +178,7 @@ class Pages {
     }
 
     if (
-      ($post->postTitle !== $this->wp->__('MailPoet Page', 'mailpoet'))
+      ($post->post_title !== $this->wp->__('MailPoet Page', 'mailpoet')) // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       ||
       ($pageTitle !== $this->wp->singlePostTitle('', false))
     ) {
diff --git a/lib/Util/ConflictResolver.php b/lib/Util/ConflictResolver.php
index a9f0a9ddf0..2016ea3ae6 100644
--- a/lib/Util/ConflictResolver.php
+++ b/lib/Util/ConflictResolver.php
@@ -80,12 +80,12 @@ class ConflictResolver {
     $_this->permittedAssetsLocations['styles'] = WPFunctions::get()->applyFilters('mailpoet_conflict_resolver_whitelist_style', $_this->permittedAssetsLocations['styles']);
     // unload all styles except from the list of allowed
     $dequeueStyles = function() use($_this) {
-      global $wpStyles;
-      if (!isset($wpStyles->registered)) return;
-      if (empty($wpStyles->queue)) return;
-      foreach ($wpStyles->queue as $wpStyle) {
-        if (empty($wpStyles->registered[$wpStyle])) continue;
-        $registeredStyle = $wpStyles->registered[$wpStyle];
+      global $wp_styles; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+      if (!isset($wp_styles->registered)) return; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+      if (empty($wp_styles->queue)) return; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+      foreach ($wp_styles->queue as $wpStyle) { // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+        if (empty($wp_styles->registered[$wpStyle])) continue; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+        $registeredStyle = $wp_styles->registered[$wpStyle]; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
         if (!is_string($registeredStyle->src)) {
           continue;
         }
@@ -111,10 +111,10 @@ class ConflictResolver {
     $_this->permittedAssetsLocations['scripts'] = WPFunctions::get()->applyFilters('mailpoet_conflict_resolver_whitelist_script', $_this->permittedAssetsLocations['scripts']);
     // unload all scripts except from the list of allowed
     $dequeueScripts = function() use($_this) {
-      global $wpScripts;
-      foreach ($wpScripts->queue as $wpScript) {
-        if (empty($wpScripts->registered[$wpScript])) continue;
-        $registeredScript = $wpScripts->registered[$wpScript];
+      global $wp_scripts; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+      foreach ($wp_scripts->queue as $wpScript) { // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+        if (empty($wp_scripts->registered[$wpScript])) continue; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+        $registeredScript = $wp_scripts->registered[$wpScript]; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
         if (!is_string($registeredScript->src)) {
           continue;
         }
@@ -139,8 +139,8 @@ class ConflictResolver {
 
     // mark editor as already enqueued to prevent loading its assets
     // when wp_enqueue_editor() used by some other plugin
-    global $wpActions;
-    $wpActions['wp_enqueue_editor'] = 1;
+    global $wp_actions; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $wp_actions['wp_enqueue_editor'] = 1; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
 
     // prevent editor loading when used wp_editor() used by some other plugin
     WPFunctions::get()->addFilter('wp_editor_settings', function () {
@@ -173,12 +173,12 @@ class ConflictResolver {
     ];
 
     $disableWpTinymce = function() use ($tinyMceFooterScriptHooks) {
-      global $wpFilter;
+      global $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       $actionName = 'admin_print_footer_scripts';
-      if (!isset($wpFilter[$actionName])) {
+      if (!isset($wp_filter[$actionName])) { // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
         return;
       }
-      foreach ($wpFilter[$actionName]->callbacks as $priority => $callbacks) {
+      foreach ($wp_filter[$actionName]->callbacks as $priority => $callbacks) { // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
         foreach ($tinyMceFooterScriptHooks as $hook) {
           if (isset($callbacks[$hook])) {
             WPFunctions::get()->removeAction($actionName, $callbacks[$hook]['function'], $priority);
diff --git a/tests/_support/DefaultsExtension.php b/tests/_support/DefaultsExtension.php
index 44f6ea3362..68078705da 100644
--- a/tests/_support/DefaultsExtension.php
+++ b/tests/_support/DefaultsExtension.php
@@ -41,9 +41,9 @@ class DefaultsExtension extends Extension { // phpcs:ignore PSR1.Classes.ClassDe
 
     // get rid of 'blog/' prefix that is added automatically to rewrite rules on multisite by default
     // (init() loads 'permalink_structure' option from DB, flush_rules() regenerates 'rewrite_rules')
-    global $wpRewrite;
-    $wpRewrite->init();
-    $wpRewrite->flush_rules();
+    global $wp_rewrite; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $wp_rewrite->init(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $wp_rewrite->flush_rules(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   private function setupWooCommerce() {
diff --git a/tests/integration/Config/InitializerTest.php b/tests/integration/Config/InitializerTest.php
index 79126c5d73..b6b32fc409 100644
--- a/tests/integration/Config/InitializerTest.php
+++ b/tests/integration/Config/InitializerTest.php
@@ -4,10 +4,10 @@ namespace MailPoet\Test\Config;
 
 class InitializerTest extends \MailPoetTest {
   public function testItConfiguresHooks() {
-    global $wpFilter;
+    global $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $isHooked = false;
     // mailpoet should hook to 'wp_loaded' with priority of 10
-    foreach ($wpFilter['wp_loaded'][10] as $name => $hook) {
+    foreach ($wp_filter['wp_loaded'][10] as $name => $hook) { // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
       if (preg_match('/postInitialize/', $name)) $isHooked = true;
     }
     expect($isHooked)->true();
diff --git a/tests/integration/Util/ConflictResolverTest.php b/tests/integration/Util/ConflictResolverTest.php
index 82da3d3a20..2d6ae077a5 100644
--- a/tests/integration/Util/ConflictResolverTest.php
+++ b/tests/integration/Util/ConflictResolverTest.php
@@ -13,8 +13,8 @@ class ConflictResolverTest extends \MailPoetTest {
     parent::__construct();
     $this->conflictResolver = new ConflictResolver();
     $this->conflictResolver->init();
-    global $wpFilter;
-    $this->wpFilter = $wpFilter;
+    global $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $this->wpFilter = $wp_filter; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   public function testItResolvesRouterUrlQueryParametersConflict() {
@@ -39,10 +39,10 @@ class ConflictResolverTest extends \MailPoetTest {
     do_action('admin_print_styles');
     do_action('admin_print_footer_scripts');
     do_action('admin_footer');
-    global $wpStyles;
+    global $wp_styles; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     // it should dequeue all styles except those found on the list of permitted locations
-    expect(in_array('select2', $wpStyles->queue))->false();
-    expect(in_array('permitted_style', $wpStyles->queue))->true();
+    expect(in_array('select2', $wp_styles->queue))->false(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    expect(in_array('permitted_style', $wp_styles->queue))->true(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   public function testItWhitelistsStyles() {
@@ -60,9 +60,9 @@ class ConflictResolverTest extends \MailPoetTest {
     do_action('admin_print_styles');
     do_action('admin_print_footer_scripts');
     do_action('admin_footer');
-    global $wpStyles;
+    global $wp_styles; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     // it should not dequeue select2 style
-    expect(in_array('select2', $wpStyles->queue))->true();
+    expect(in_array('select2', $wp_styles->queue))->true(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   public function testItUnloadsAllScriptsFromLocationsNotOnPermittedList() {
@@ -76,11 +76,11 @@ class ConflictResolverTest extends \MailPoetTest {
     $this->conflictResolver->resolveScriptsConflict();
     do_action('wp_print_scripts');
     do_action('admin_print_footer_scripts');
-    global $wpScripts;
+    global $wp_scripts; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     // it should dequeue all scripts except those found on the list of permitted locations
-    expect(in_array('select2', $wpScripts->queue))->false();
-    expect(in_array('some_random_script', $wpScripts->queue))->false();
-    expect(in_array('permitted_script', $wpScripts->queue))->true();
+    expect(in_array('select2', $wp_scripts->queue))->false(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    expect(in_array('some_random_script', $wp_scripts->queue))->false(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    expect(in_array('permitted_script', $wp_scripts->queue))->true(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   public function testItWhitelistsScripts() {
@@ -96,11 +96,11 @@ class ConflictResolverTest extends \MailPoetTest {
     $this->conflictResolver->resolveStylesConflict();
     do_action('wp_print_scripts');
     do_action('admin_print_footer_scripts');
-    global $wpScripts;
+    global $wp_scripts; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     // it should not dequeue select2 script
-    expect(in_array('select2', $wpScripts->queue))->true();
+    expect(in_array('select2', $wp_scripts->queue))->true(); // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 
   public function _after() {
   }
-}
\ No newline at end of file
+}
diff --git a/tests/integration/WP/FunctionsTest.php b/tests/integration/WP/FunctionsTest.php
index a6b4cffc6f..df1eb2e917 100644
--- a/tests/integration/WP/FunctionsTest.php
+++ b/tests/integration/WP/FunctionsTest.php
@@ -12,9 +12,9 @@ class FunctionsTest extends \MailPoetTest {
   public $contentWidth;
   public function _before() {
     parent::_before();
-    global $contentWidth;
-    $this->contentWidth = $contentWidth;
-    $contentWidth = 150;
+    global $content_width; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $this->contentWidth = $content_width; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $content_width = 150; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
     $this->action = 'mailpoet_test_action';
     $this->filter = 'mailpoet_test_filter';
     $this->wp = new WPFunctions;
@@ -93,7 +93,7 @@ class FunctionsTest extends \MailPoetTest {
   }
 
   public function _after() {
-    global $contentWidth;
-    $contentWidth = $this->contentWidth;
+    global $content_width; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
+    $content_width = $this->contentWidth; // phpcs:ignore Squiz.NamingConventions.ValidVariableName.NotCamelCaps
   }
 }