diff --git a/Classes/Channel.php b/Classes/Channel.php
index 6d7781a..f11364a 100644
--- a/Classes/Channel.php
+++ b/Classes/Channel.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace RobertLemke\Rss;
 
 /*
@@ -16,7 +18,6 @@
  */
 class Channel
 {
-
     /**
      * @var string
      */
@@ -37,11 +38,6 @@ class Channel
      */
     protected $websiteUri;
 
-    /**
-     * @var string
-     */
-    protected $imageUri;
-
     /**
      * @var string
      */
@@ -50,68 +46,75 @@ class Channel
     /**
      * @var array
      */
-    protected $items = array();
+    protected $items = [];
 
     /**
      * @param string $description
-     * @return void
+     * @return Channel
      */
-    public function setDescription($description)
+    public function setDescription(string $description): Channel
     {
         $this->description = $description;
+        return $this;
     }
 
     /**
      * @param string $title
-     * @return void
+     * @return Channel
      */
-    public function setTitle($title)
+    public function setTitle(string $title): Channel
     {
         $this->title = $title;
+        return $this;
     }
 
     /**
      * @param string $feedUri
-     * @return void
+     * @return Channel
      */
-    public function setFeedUri($feedUri)
+    public function setFeedUri(string $feedUri): Channel
     {
         $this->feedUri = $feedUri;
+        return $this;
     }
 
     /**
      * @param string $websiteUri
-     * @return void
+     * @return Channel
      */
-    public function setWebsiteUri($websiteUri)
+    public function setWebsiteUri(string $websiteUri): Channel
     {
         $this->websiteUri = $websiteUri;
+        return $this;
     }
 
     /**
      * @param string $language
-     * @return void
+     * @return Channel
      */
-    public function setLanguage($language)
+    public function setLanguage(string $language): Channel
     {
         $this->language = $language;
+        return $this;
     }
 
     /**
      * Adds a new item to this channel
      *
      * @param Item $item An item
-     * @return void
+     * @return Channel
      */
-    public function addItem(Item $item)
+    public function addItem(Item $item): Channel
     {
         $this->items[] = $item;
+        return $this;
     }
 
     /**
      * @return \SimpleXMLElement
+     * @throws \Exception
      */
-    public function asXML()
+    public function asXML(): \SimpleXMLElement
     {
         $date = new \DateTime('now', new \DateTimeZone('GMT'));
         $nowFormatted = $date->format('D, d M Y H:i:s') . ' GMT';
@@ -148,4 +151,4 @@ public function asXML()
 
         return $xml;
     }
-}
\ No newline at end of file
+}
diff --git a/Classes/Feed.php b/Classes/Feed.php
index 02fdbf5..2f6f500 100644
--- a/Classes/Feed.php
+++ b/Classes/Feed.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace RobertLemke\Rss;
 
 /*
@@ -16,11 +18,10 @@
  */
 class Feed
 {
-
     /**
      * @var array<Channel>
      */
-    protected $channels = array();
+    protected $channels = [];
 
     /**
      * Adds a new channel to this feed
@@ -28,7 +29,7 @@ class Feed
      * @param Channel $channel
      * @return Feed
      */
-    public function addChannel(Channel $channel)
+    public function addChannel(Channel $channel): Feed
     {
         $this->channels[] = $channel;
 
@@ -40,7 +41,7 @@ public function addChannel(Channel $channel)
      *
      * @return string
      */
-    public function render()
+    public function render(): string
     {
         $xml = new SimpleXMLElement(
             '<?xml version="1.0" encoding="UTF-8" ?>
@@ -67,4 +68,4 @@ public function render()
 
         return $dom->saveXML();
     }
-}
\ No newline at end of file
+}
diff --git a/Classes/Item.php b/Classes/Item.php
index 85b9bfd..56b872f 100644
--- a/Classes/Item.php
+++ b/Classes/Item.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace RobertLemke\Rss;
 
 /*
@@ -16,7 +18,6 @@
  */
 class Item
 {
-
     /**
      * @var string
      */
@@ -60,159 +61,168 @@ class Item
     /**
      * @var array<string>
      */
-    protected $categories = array();
+    protected $categories = [];
 
     /**
      * Can be an array of either strings or arrays (with indexes "category" and "domain").
      *
      * @param array $categories
-     * @return void
+     * @return Item
      */
-    public function setCategories($categories)
+    public function setCategories(array $categories): Item
     {
         $this->categories = $categories;
+        return $this;
     }
 
     /**
      * @return array
      */
-    public function getCategories()
+    public function getCategories(): array
     {
         return $this->categories;
     }
 
     /**
      * @param string $commentsLink
-     * @return void
+     * @return Item
      */
-    public function setCommentsLink($commentsLink)
+    public function setCommentsLink(string $commentsLink): Item
     {
         $this->commentsLink = $commentsLink;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getCommentsLink()
+    public function getCommentsLink(): string
     {
         return $this->commentsLink;
     }
 
     /**
      * @param string $content
-     * @return void
+     * @return Item
      */
-    public function setContent($content)
+    public function setContent(string $content): Item
     {
         $this->content = $content;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getContent()
+    public function getContent(): string
     {
         return $this->content;
     }
 
     /**
      * @param string $creator
-     * @return void
+     * @return Item
      */
-    public function setCreator($creator)
+    public function setCreator(string $creator): Item
     {
         $this->creator = $creator;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getCreator()
+    public function getCreator(): string
     {
         return $this->creator;
     }
 
     /**
      * @param string $description
-     * @return void
+     * @return Item
      */
-    public function setDescription($description)
+    public function setDescription(string $description): Item
     {
         $this->description = $description;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getDescription()
+    public function getDescription(): string
     {
         return $this->description;
     }
 
     /**
      * @param string $guid
-     * @return void
+     * @return Item
      */
-    public function setGuid($guid)
+    public function setGuid(string $guid): Item
     {
         $this->guid = $guid;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getGuid()
+    public function getGuid(): string
     {
         return $this->guid;
     }
 
     /**
      * @param string $itemLink
-     * @return void
+     * @return Item
      */
-    public function setItemLink($itemLink)
+    public function setItemLink(string $itemLink): Item
     {
         $this->itemLink = $itemLink;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getItemLink()
+    public function getItemLink(): string
     {
         return $this->itemLink;
     }
 
     /**
      * @param \DateTime $publicationDate
-     * @return void
+     * @return Item
      */
-    public function setPublicationDate(\DateTime $publicationDate = null)
+    public function setPublicationDate(\DateTime $publicationDate = null): Item
     {
         $this->publicationDate = $publicationDate;
+        return $this;
     }
 
     /**
      * @return \DateTime
      */
-    public function getPublicationDate()
+    public function getPublicationDate(): \DateTime
     {
         return $this->publicationDate;
     }
 
     /**
      * @param string $title
-     * @return void
+     * @return Item
      */
-    public function setTitle($title)
+    public function setTitle(string $title): Item
     {
         $this->title = $title;
+        return $this;
     }
 
     /**
      * @return string
      */
-    public function getTitle()
+    public function getTitle(): string
     {
         return $this->title;
     }
@@ -220,7 +230,7 @@ public function getTitle()
     /**
      * @return \SimpleXMLElement
      */
-    public function asXml()
+    public function asXml(): \SimpleXMLElement
     {
         $xml = new SimpleXMLElement(
             '<?xml version="1.0" encoding="UTF-8" ?>
@@ -267,5 +277,4 @@ public function asXml()
 
         return $xml;
     }
-
-}
\ No newline at end of file
+}
diff --git a/Classes/SimpleXMLElement.php b/Classes/SimpleXMLElement.php
index a4afc05..f1195c5 100644
--- a/Classes/SimpleXMLElement.php
+++ b/Classes/SimpleXMLElement.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace RobertLemke\Rss;
 
 /*
@@ -16,14 +18,13 @@
  */
 class SimpleXMLElement extends \SimpleXMLElement
 {
-
     /**
      * Adds a new child node - and replaces "&" by "&amp;" on the way ...
      *
      * @param string $name Name of the tag
      * @param string $value The tag value, if any
      * @param string $namespace The tag namespace, if any
-     * @return SimpleXMLElement
+     * @return \SimpleXMLElement
      */
     public function addChild($name, $value = null, $namespace = null)
     {
@@ -49,9 +50,9 @@ public function addAttribute($name, $value = null, $namespace = null)
      * @param string $name tag name
      * @param string $value tag value
      * @param string $namespace The tag namespace, if any
-     * @return SimpleXMLElement
+     * @return \SimpleXMLElement
      */
-    public function addCdataChild($name, $value, $namespace = null)
+    public function addCdataChild(string $name, string $value, string $namespace = null): SimpleXMLElement
     {
         $child = $this->addChild($name, null, $namespace);
         $child->setChildCdataValue($value);
@@ -64,10 +65,10 @@ public function addCdataChild($name, $value, $namespace = null)
      * @param string $value The value to be enclosed in CDATA
      * @return void
      */
-    private function setChildCdataValue($value)
+    private function setChildCdataValue(string $value): void
     {
         $domNode = dom_import_simplexml($this);
         $domNode->appendChild($domNode->ownerDocument->createCDATASection($value));
     }
 
-}
\ No newline at end of file
+}
diff --git a/README.md b/README.md
index 3d18bcf..0a4cd5b 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 RSS / Atom Feed Generator
 =========================
 
-This is yet another RSS / Atom feed generator for PHP 5.5 and later. It works great
+This is yet another RSS / Atom feed generator for PHP 7 and later. It works great
 in combination with Flow but should also be fine as a standalone library.
 
 This package is composer enabled.
@@ -12,26 +12,26 @@ Example
 ```php
 <?php
 
-$feed = new Feed();
+$feed = new \RobertLemke\Rss\Feed();
 
-$channel = new Channel();
+$channel = new \RobertLemke\Rss\Channel();
 $channel
-  ->setTitle('All about TYPO3 Flow')
+  ->setTitle('All about Neos Flow')
   ->setDescription($channelDescription)
   ->setFeedUri($feedUri)
   ->setWebsiteUri($websiteUri)
   ->setLanguage('en-US');
 
-$item = new Item();
+$item = new \RobertLemke\Rss\Item();
 $item
   ->setTitle('My first blog post')
   ->setGuid($someUniqueIdentifier)
-  ->setPublicationDate(new \DateTime())
+  ->setPublicationDate(new DateTime())
   ->setContent($blogPostContent);
 
 $channel->addItem($item);
 $feed->addChannel($channel);
 
-echo $feed;
+echo $feed->render();
 
 ```
diff --git a/composer.json b/composer.json
index a2b1a64..ac6a6a2 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,9 @@
         }
     ],
     "require": {
-        "php": "~5.5 || ~7.0"
+        "ext-simplexml": "*",
+        "ext-dom": "*",
+        "php": "~7.0"
     },
     "conflict": {
         "neos/flow": "<4"