PHP 5.4 supports $this with closures.

extensions/mutex/yii/mutex/Mutex.php

@@ -34,11 +34,10 @@ abstract class Mutex extends Component
 	public function init()
 	{
 		if ($this->autoRelease) {
-			$mutex = $this;
 			$locks = &$this->_locks;
-			register_shutdown_function(function () use ($mutex, &$locks) {
+			register_shutdown_function(function () use ($this, &$locks) {
 				foreach ($locks as $lock) {
-					$mutex->release($lock);
+					$this->release($lock);
 				}
 			});
 		}

framework/yii/base/ErrorHandler.php

@@ -175,10 +175,9 @@ class ErrorHandler extends Component
 			$html = rtrim($html, '\\');
 		} elseif (strpos($code, '()') !== false) {
 			// method/function call
-			$self = $this;
-			$html = preg_replace_callback('/^(.*)\(\)$/', function ($matches) use ($self) {
-				return '<a href="http://yiiframework.com/doc/api/2.0/' . $self->htmlEncode($matches[1]) . '" target="_blank">' .
-					$self->htmlEncode($matches[1]) . '</a>()';
+			$html = preg_replace_callback('/^(.*)\(\)$/', function ($matches) use ($this) {
+				return '<a href="http://yiiframework.com/doc/api/2.0/' . $this->htmlEncode($matches[1]) . '" target="_blank">' .
+					$this->htmlEncode($matches[1]) . '</a>()';
 			}, $code);
 		}
 		return $html;

framework/yii/db/Connection.php

@@ -508,13 +508,12 @@ class Connection extends Component
 	 */
 	public function quoteSql($sql)
 	{
-		$db = $this;
 		return preg_replace_callback('/(\\{\\{(%?[\w\-\. ]+%?)\\}\\}|\\[\\[([\w\-\. ]+)\\]\\])/',
-			function ($matches) use ($db) {
+			function ($matches) use ($this) {
 				if (isset($matches[3])) {
-					return $db->quoteColumnName($matches[3]);
+					return $this->quoteColumnName($matches[3]);
 				} else {
-					return str_replace('%', $db->tablePrefix, $db->quoteTableName($matches[2]));
+					return str_replace('%', $this->tablePrefix, $this->quoteTableName($matches[2]));
 				}
 			}, $sql);
 	}

framework/yii/debug/Module.php

@@ -57,9 +57,8 @@ class Module extends \yii\base\Module
 		$this->dataPath = Yii::getAlias($this->dataPath);
 		$this->logTarget = Yii::$app->getLog()->targets['debug'] = new LogTarget($this);
 		// do not initialize view component before application is ready (needed when debug in preload)
-		$module = $this;
-		Yii::$app->on(Application::EVENT_BEFORE_ACTION, function() use ($module) {
-			Yii::$app->getView()->on(View::EVENT_END_BODY, array($module, 'renderToolbar'));
+		Yii::$app->on(Application::EVENT_BEFORE_ACTION, function() use ($this) {
+			Yii::$app->getView()->on(View::EVENT_END_BODY, array($this, 'renderToolbar'));
 		});
 
 		foreach (array_merge($this->corePanels(), $this->panels) as $id => $config) {

framework/yii/grid/ActionColumn.php

@@ -88,11 +88,10 @@ class ActionColumn extends Column
 	 */
 	protected function renderDataCellContent($model, $index)
 	{
-		$column = $this;
-		return preg_replace_callback('/\\{(\w+)\\}/', function ($matches) use ($model, $column) {
+		return preg_replace_callback('/\\{(\w+)\\}/', function ($matches) use ($this, $model) {
 			$name = $matches[1];
-			if (isset($column->buttons[$name])) {
-				return call_user_func($column->buttons[$name], $model, $column);
+			if (isset($this->buttons[$name])) {
+				return call_user_func($this->buttons[$name], $model, $this);
 			} else {
 				return '';
 			}

framework/yii/widgets/BaseListView.php

@@ -92,9 +92,8 @@ abstract class BaseListView extends Widget
 	public function run()
 	{
 		if ($this->dataProvider->getCount() > 0 || $this->empty === false) {
-			$widget = $this;
-			$content = preg_replace_callback("/{\\w+}/", function ($matches) use ($widget) {
-				$content = $widget->renderSection($matches[0]);
+			$content = preg_replace_callback("/{\\w+}/", function ($matches) use ($this) {
+				$content = $this->renderSection($matches[0]);
 				return $content === false ? $matches[0] : $content;
 			}, $this->layout);
 		} else {