diff --git a/build/controllers/PhpDocController.php b/build/controllers/PhpDocController.php
index 9aedda1a47..f8cee3f7d3 100644
--- a/build/controllers/PhpDocController.php
+++ b/build/controllers/PhpDocController.php
@@ -172,7 +172,7 @@ class PhpDocController extends Controller
                     $except[] = "/extensions/$ext$path";
                 }
             }
-        } elseif (preg_match('~extensions/([\w\d-]+)[\\\\/]?$~', $root, $matches)) {
+        } elseif (preg_match('~extensions/([\w-]+)[\\\\/]?$~', $root, $matches)) {
 
             $extensionPath = dirname(rtrim($root, '\\/'));
             $this->setUpExtensionAliases($extensionPath);
@@ -196,7 +196,7 @@ class PhpDocController extends Controller
 //            if ($extension === 'composer') {
 //                return [];
 //            }
-        } elseif (preg_match('~apps/([\w\d-]+)[\\\\/]?$~', $root, $matches)) {
+        } elseif (preg_match('~apps/([\w-]+)[\\\\/]?$~', $root, $matches)) {
 
             $extensionPath = dirname(dirname(rtrim($root, '\\/'))) . '/extensions';
             $this->setUpExtensionAliases($extensionPath);
diff --git a/framework/db/pgsql/QueryBuilder.php b/framework/db/pgsql/QueryBuilder.php
index fb3330eae7..77b3ae91df 100644
--- a/framework/db/pgsql/QueryBuilder.php
+++ b/framework/db/pgsql/QueryBuilder.php
@@ -188,7 +188,7 @@ class QueryBuilder extends \yii\db\QueryBuilder
     public function checkIntegrity($check = true, $schema = '', $table = '')
     {
         $enable = $check ? 'ENABLE' : 'DISABLE';
-        $schema = $schema ? $schema : $this->db->getSchema()->defaultSchema;
+        $schema = $schema ?: $this->db->getSchema()->defaultSchema;
         $tableNames = $table ? [$table] : $this->db->getSchema()->getTableNames($schema);
         $viewNames = $this->db->getSchema()->getViewNames($schema);
         $tableNames = array_diff($tableNames, $viewNames);
diff --git a/framework/i18n/I18N.php b/framework/i18n/I18N.php
index c8e87d1437..36bc1aecad 100644
--- a/framework/i18n/I18N.php
+++ b/framework/i18n/I18N.php
@@ -109,7 +109,7 @@ class I18N extends Component
             return $message;
         }
 
-        if (preg_match('~{\s*[\d\w]+\s*,~u', $message)) {
+        if (preg_match('~{\s*[\w]+\s*,~u', $message)) {
             $formatter = $this->getMessageFormatter();
             $result = $formatter->format($message, $params, $language);
             if ($result === false) {
diff --git a/framework/rbac/DbManager.php b/framework/rbac/DbManager.php
index b66f6e4da9..fca49eee35 100644
--- a/framework/rbac/DbManager.php
+++ b/framework/rbac/DbManager.php
@@ -480,7 +480,7 @@ class DbManager extends BaseManager
     {
         $role = $this->getRole($roleName);
 
-        if (is_null($role)) {
+        if ($role === null) {
             throw new InvalidParamException("Role \"$roleName\" not found.");
         }
 
diff --git a/framework/rbac/PhpManager.php b/framework/rbac/PhpManager.php
index fcb328183c..d489a751fd 100644
--- a/framework/rbac/PhpManager.php
+++ b/framework/rbac/PhpManager.php
@@ -410,7 +410,7 @@ class PhpManager extends BaseManager
     {
         $role = $this->getRole($roleName);
 
-        if (is_null($role)) {
+        if ($role === null) {
             throw new InvalidParamException("Role \"$roleName\" not found.");
         }
 
diff --git a/framework/validators/IpValidator.php b/framework/validators/IpValidator.php
index 55f762006c..6533e7556f 100644
--- a/framework/validators/IpValidator.php
+++ b/framework/validators/IpValidator.php
@@ -527,7 +527,7 @@ class IpValidator extends Validator
      */
     private function getIpParsePattern()
     {
-        return '/^(' . preg_quote(static::NEGATION_CHAR) . '?)(.+?)(\/(\d+))?$/';
+        return '/^(' . preg_quote(static::NEGATION_CHAR, '/') . '?)(.+?)(\/(\d+))?$/';
     }
 
     /**
diff --git a/framework/web/MultipartFormDataParser.php b/framework/web/MultipartFormDataParser.php
index 7b34f06dd7..6fae328d9b 100644
--- a/framework/web/MultipartFormDataParser.php
+++ b/framework/web/MultipartFormDataParser.php
@@ -132,7 +132,7 @@ class MultipartFormDataParser extends Object implements RequestParserInterface
         }
         $boundary = $matches[1];
 
-        $bodyParts = preg_split('/\\R?-+' . preg_quote($boundary) . '/s', $rawBody);
+        $bodyParts = preg_split('/\\R?-+' . preg_quote($boundary, '/') . '/s', $rawBody);
         array_pop($bodyParts); // last block always has no data, contains boundary ending like `--`
 
         $bodyParams = [];