diff --git a/Button.php b/Button.php
index 0c21a3e..0dc25a9 100644
--- a/Button.php
+++ b/Button.php
@@ -56,7 +56,7 @@ class Button extends Widget
      */
     public function run()
     {
-        echo Html::tag($this->tagName, $this->encodeLabel ? Html::encode($this->label) : $this->label, $this->options);
         $this->registerPlugin('button');
+        return Html::tag($this->tagName, $this->encodeLabel ? Html::encode($this->label) : $this->label, $this->options);
     }
 }
diff --git a/ButtonDropdown.php b/ButtonDropdown.php
index 3563d71..3d74a5b 100644
--- a/ButtonDropdown.php
+++ b/ButtonDropdown.php
@@ -79,11 +79,13 @@ class ButtonDropdown extends Widget
         $options = $this->containerOptions;
         $tag = ArrayHelper::remove($options, 'tag', 'div');
 
-        echo Html::beginTag($tag, $this->containerOptions);
-        echo "\n" . $this->renderButton();
-        echo "\n" . $this->renderDropdown();
-        echo "\n" . Html::endTag($tag);
         $this->registerPlugin('button');
+        return implode("\n", [
+            Html::beginTag($tag, $this->containerOptions),
+            $this->renderButton(),
+            $this->renderDropdown(),
+            Html::endTag($tag)
+        ]);
     }
 
     /**
diff --git a/ButtonGroup.php b/ButtonGroup.php
index 91bed41..c4459a0 100644
--- a/ButtonGroup.php
+++ b/ButtonGroup.php
@@ -67,8 +67,8 @@ class ButtonGroup extends Widget
      */
     public function run()
     {
-        echo Html::tag('div', $this->renderButtons(), $this->options);
         BootstrapAsset::register($this->getView());
+        return Html::tag('div', $this->renderButtons(), $this->options);
     }
 
     /**
diff --git a/Carousel.php b/Carousel.php
index 68c3def..468b316 100644
--- a/Carousel.php
+++ b/Carousel.php
@@ -81,12 +81,14 @@ class Carousel extends Widget
      */
     public function run()
     {
-        echo Html::beginTag('div', $this->options) . "\n";
-        echo $this->renderIndicators() . "\n";
-        echo $this->renderItems() . "\n";
-        echo $this->renderControls() . "\n";
-        echo Html::endTag('div') . "\n";
         $this->registerPlugin('carousel');
+        return implode("\n", [
+            Html::beginTag('div', $this->options),
+            $this->renderIndicators(),
+            $this->renderItems(),
+            $this->renderControls(),
+            Html::endTag('div')
+        ]);
     }
 
     /**
diff --git a/Collapse.php b/Collapse.php
index 22e022e..0222a5a 100644
--- a/Collapse.php
+++ b/Collapse.php
@@ -76,10 +76,12 @@ class Collapse extends Widget
      */
     public function run()
     {
-        echo Html::beginTag('div', $this->options) . "\n";
-        echo $this->renderItems() . "\n";
-        echo Html::endTag('div') . "\n";
         $this->registerPlugin('collapse');
+        return implode("\n", [
+            Html::beginTag('div', $this->options),
+            $this->renderItems(),
+            Html::endTag('div')
+        ]);
     }
 
     /**
diff --git a/Dropdown.php b/Dropdown.php
index 14fc158..7537b7b 100644
--- a/Dropdown.php
+++ b/Dropdown.php
@@ -73,9 +73,9 @@ class Dropdown extends Widget
      */
     public function run()
     {
-        echo $this->renderItems($this->items, $this->options);
         BootstrapPluginAsset::register($this->getView());
         $this->registerClientEvents();
+        return $this->renderItems($this->items, $this->options);
     }
 
     /**
diff --git a/Nav.php b/Nav.php
index bfeb606..e5d132f 100644
--- a/Nav.php
+++ b/Nav.php
@@ -115,8 +115,8 @@ class Nav extends Widget
      */
     public function run()
     {
-        echo $this->renderItems();
         BootstrapAsset::register($this->getView());
+        return $this->renderItems();
     }
 
     /**
diff --git a/Progress.php b/Progress.php
index dbeed97..4e7d903 100644
--- a/Progress.php
+++ b/Progress.php
@@ -105,10 +105,12 @@ class Progress extends Widget
      */
     public function run()
     {
-        echo Html::beginTag('div', $this->options) . "\n";
-        echo $this->renderProgress() . "\n";
-        echo Html::endTag('div') . "\n";
         BootstrapAsset::register($this->getView());
+        return implode("\n", [
+            Html::beginTag('div', $this->options),
+            $this->renderProgress(),
+            Html::endTag('div')
+        ]);
     }
 
     /**