Compare with null instead of isset

framework/console/Request.php

@@ -29,7 +29,7 @@ class Request extends \yii\base\Request
      */
     public function getParams()
     {
-        if (!isset($this->_params)) {
+        if ($this->_params === null) {
             if (isset($_SERVER['argv'])) {
                 $this->_params = $_SERVER['argv'];
                 array_shift($this->_params);

framework/filters/AccessControl.php

@@ -120,7 +120,7 @@ class AccessControl extends ActionFilter
             } elseif ($allow === false) {
                 if (isset($rule->denyCallback)) {
                     call_user_func($rule->denyCallback, $rule, $action);
-                } elseif (isset($this->denyCallback)) {
+                } elseif ($this->denyCallback !== null) {
                     call_user_func($this->denyCallback, $rule, $action);
                 } else {
                     $this->denyAccess($user);
@@ -128,7 +128,7 @@ class AccessControl extends ActionFilter
                 return false;
             }
         }
-        if (isset($this->denyCallback)) {
+        if ($this->denyCallback !== null) {
             call_user_func($this->denyCallback, null, $action);
         } else {
             $this->denyAccess($user);

framework/test/ActiveFixture.php

@@ -57,7 +57,7 @@ class ActiveFixture extends BaseActiveFixture
     public function init()
     {
         parent::init();
-        if (!isset($this->modelClass) && !isset($this->tableName)) {
+        if ($this->modelClass === null && $this->tableName === null) {
             throw new InvalidConfigException('Either "modelClass" or "tableName" must be set.');
         }
     }

framework/web/DbSession.php

@@ -139,7 +139,7 @@ class DbSession extends MultiFieldSession
         $query->from($this->sessionTable)
             ->where('[[expire]]>:expire AND [[id]]=:id', [':expire' => time(), ':id' => $id]);
 
-        if (isset($this->readCallback)) {
+        if ($this->readCallback !== null) {
             $fields = $query->one($this->db);
             return $fields === false ? '' : $this->extractData($fields);
         }

framework/web/MultiFieldSession.php

@@ -98,7 +98,7 @@ abstract class MultiFieldSession extends Session
         $fields = [
             'data' => $data,
         ];
-        if (isset($this->writeCallback)) {
+        if ($this->writeCallback !== null) {
             $fields = array_merge(
                 $fields,
                 call_user_func($this->writeCallback, $this)
@@ -123,7 +123,7 @@ abstract class MultiFieldSession extends Session
      */
     protected function extractData($fields)
     {
-        if (isset($this->readCallback)) {
+        if ($this->readCallback !== null) {
             if (!isset($fields['data'])) {
                 $fields['data'] = '';
             }

framework/yii

@@ -31,7 +31,7 @@ $application = new yii\console\Application([
     'basePath' => __DIR__ . '/console',
     'controllerNamespace' => 'yii\console\controllers',
 ]);
-if (isset($vendorPath)) {
+if ($vendorPath !== null) {
     $application->setVendorPath($vendorPath);
 }
 $exitCode = $application->run();