diff --git a/src/ActionConfirmation.php b/src/ActionConfirmation.php
index 4926d51..c95cc06 100644
--- a/src/ActionConfirmation.php
+++ b/src/ActionConfirmation.php
@@ -140,11 +140,17 @@ public function setDismissText($dismissText)
      */
     public function toArray()
     {
-        return [
+        $ret = [
             'title' => $this->getTitle(),
             'text' => $this->getText(),
             'ok_text' => $this->getOkText(),
             'dismiss_text' => $this->getDismissText(),
         ];
+
+        $ret = array_filter($ret, function($item) {
+            return !empty($item);
+        });
+
+        return $ret;
     }
 }
diff --git a/src/Attachment.php b/src/Attachment.php
index 734a01b..450ff7b 100644
--- a/src/Attachment.php
+++ b/src/Attachment.php
@@ -13,6 +13,13 @@ class Attachment
      */
     protected $fallback;
 
+    /**
+     * The callback_id
+     *
+     * @var string
+     */
+    protected $callback_id;
+
     /**
      * Optional text that should appear within the attachment.
      *
@@ -139,6 +146,10 @@ public function __construct(array $attributes)
             $this->setFallback($attributes['fallback']);
         }
 
+        if (isset($attributes['callback_id'])) {
+            $this->setCallbackId($attributes['callback_id']);
+        }
+
         if (isset($attributes['text'])) {
             $this->setText($attributes['text']);
         }
@@ -227,6 +238,29 @@ public function setFallback($fallback)
         return $this;
     }
 
+
+    /**
+     * Get the callback_id.
+     *
+     * @return string
+     */
+    public function getCallbackId() {
+        return $this->callback_id;
+    }
+
+
+    /**
+     * Set the callback_id.
+     *
+     * @param string $fallback
+     * @return $this
+     */
+    public function setCallbackId($callback_id) {
+        $this->callback_id = $callback_id;
+
+        return $this;
+    }
+
     /**
      * Get the optional text to appear within the attachment.
      *
@@ -679,18 +713,19 @@ public function addAction($action)
     public function toArray()
     {
         $data = [
-            'fallback' => $this->getFallback(),
-            'text' => $this->getText(),
-            'pretext' => $this->getPretext(),
-            'color' => $this->getColor(),
-            'footer' => $this->getFooter(),
+            'fallback'    => $this->getFallback(),
+            'callback_id' => $this->getCallbackId(),
+            'text'        => $this->getText(),
+            'pretext'     => $this->getPretext(),
+            'color'       => $this->getColor(),
+            'footer'      => $this->getFooter(),
             'footer_icon' => $this->getFooterIcon(),
-            'ts' => $this->getTimestamp() ? $this->getTimestamp()->getTimestamp() : null,
-            'mrkdwn_in' => $this->getMarkdownFields(),
-            'image_url' => $this->getImageUrl(),
-            'thumb_url' => $this->getThumbUrl(),
-            'title' => $this->getTitle(),
-            'title_link' => $this->getTitleLink(),
+            'ts'          => $this->getTimestamp() ? $this->getTimestamp()->getTimestamp() : null,
+            'mrkdwn_in'   => $this->getMarkdownFields(),
+            'image_url'   => $this->getImageUrl(),
+            'thumb_url'   => $this->getThumbUrl(),
+            'title'       => $this->getTitle(),
+            'title_link'  => $this->getTitleLink(),
             'author_name' => $this->getAuthorName(),
             'author_link' => $this->getAuthorLink(),
             'author_icon' => $this->getAuthorIcon(),
@@ -699,6 +734,10 @@ public function toArray()
         $data['fields'] = $this->getFieldsAsArrays();
         $data['actions'] = $this->getActionsAsArrays();
 
+        $data = array_filter($data, function($item) {
+            return !empty($item);
+        });
+
         return $data;
     }
 
diff --git a/src/AttachmentAction.php b/src/AttachmentAction.php
index fe38073..9e8864a 100644
--- a/src/AttachmentAction.php
+++ b/src/AttachmentAction.php
@@ -216,13 +216,23 @@ public function setConfirm($confirm)
      */
     public function toArray()
     {
-        return [
-            'name' => $this->getName(),
-            'text' => $this->getText(),
-            'style' => $this->getStyle(),
-            'type' => $this->getType(),
-            'value' => $this->getValue(),
-            'confirm' => $this->getConfirm()->toArray(),
+        $_confirm = $this->getConfirm();
+        $ret = [
+            'name'    => $this->getName(),
+            'text'    => $this->getText(),
+            'style'   => $this->getStyle(),
+            'type'    => $this->getType(),
+            'value'   => $this->getValue(),
         ];
+
+        if ($_confirm) {
+            $ret['confirm'] = $_confirm->toArray();
+        }
+
+        $ret = array_filter($ret, function($item) {
+            return !empty($item);
+        });
+
+        return $ret;
     }
 }
diff --git a/src/AttachmentField.php b/src/AttachmentField.php
index 166e711..784f0bf 100644
--- a/src/AttachmentField.php
+++ b/src/AttachmentField.php
@@ -125,10 +125,16 @@ public function setShort($value)
      */
     public function toArray()
     {
-        return [
+        $ret = [
             'title' => $this->getTitle(),
             'value' => $this->getValue(),
             'short' => $this->getShort(),
         ];
+
+        $ret = array_filter($ret, function($item) {
+            return !empty($item);
+        });
+
+        return $ret;
     }
 }
diff --git a/src/Client.php b/src/Client.php
index 75497f4..251354a 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -360,19 +360,30 @@ public function createMessage()
      * Send a message.
      *
      * @param \Maknz\Slack\Message $message
-     * @return void
+     * @param bool $web_api Incoming web hook or Web API
+     * @return \Psr\Http\Message\ResponseInterface
      */
-    public function sendMessage(Message $message)
+    public function sendMessage(Message $message, $web_api = false)
     {
         $payload = $this->preparePayload($message);
 
-        $encoded = json_encode($payload, JSON_UNESCAPED_UNICODE);
-
-        if ($encoded === false) {
-            throw new RuntimeException(sprintf('JSON encoding error %s: %s', json_last_error(), json_last_error_msg()));
+        if ($web_api) {
+            foreach ($payload as $key => $p) {
+                if (is_array($p)) {
+                    $payload[$key] = json_encode($p, JSON_UNESCAPED_UNICODE);
+                }
+            }
+            return $this->guzzle->post($this->endpoint, ['form_params' => $payload]);
         }
+        else {
+            $encoded = json_encode($payload, JSON_UNESCAPED_UNICODE);
+
+            if ($encoded === false) {
+                throw new RuntimeException(sprintf('JSON encoding error %s: %s', json_last_error(), json_last_error_msg()));
+            }
 
-        $this->guzzle->post($this->endpoint, ['body' => $encoded]);
+            return $this->guzzle->post($this->endpoint, ['body' => $encoded]);
+        }
     }
 
     /**
@@ -399,6 +410,10 @@ public function preparePayload(Message $message)
 
         $payload['attachments'] = $this->getAttachmentsAsArrays($message);
 
+        $payload = array_filter($payload, function($item) {
+            return !empty($item);
+        });
+
         return $payload;
     }