diff --git a/Strategy/ComparatorInterface.php b/Strategy/ComparatorInterface.php
new file mode 100644
index 0000000..468a614
--- /dev/null
+++ b/Strategy/ComparatorInterface.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace DesignPatterns\Strategy;
+
+/**
+ * Class ComparatorInterface
+ */
+interface ComparatorInterface
+{
+    /**
+     * @param mixed $a
+     * @param mixed $b
+     *
+     * @return bool
+     */
+    public function compare($a, $b);
+}
diff --git a/Strategy/DateComparator.php b/Strategy/DateComparator.php
new file mode 100644
index 0000000..9025acc
--- /dev/null
+++ b/Strategy/DateComparator.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace DesignPatterns\Strategy;
+
+/**
+ * Class DateComparator
+ */
+class DateComparator implements ComparatorInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function compare($a, $b)
+    {
+        $aDate = strtotime($a['date']);
+        $bDate = strtotime($b['date']);
+
+        if ($aDate == $bDate) {
+            return 0;
+        } else {
+            return $aDate < $bDate ? -1 : 1;
+        }
+    }
+}
diff --git a/Strategy/IdComparator.php b/Strategy/IdComparator.php
new file mode 100644
index 0000000..c3bc9a7
--- /dev/null
+++ b/Strategy/IdComparator.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace DesignPatterns\Strategy;
+
+/**
+ * Class IdComparator
+ */
+class IdComparator implements ComparatorInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function compare($a, $b)
+    {
+        if ($a['id'] == $b['id']) {
+            return 0;
+        } else {
+            return $a['id'] < $b['id'] ? -1 : 1;
+        }
+    }
+}
diff --git a/Strategy/ObjectCollection.php b/Strategy/ObjectCollection.php
new file mode 100644
index 0000000..682a8d0
--- /dev/null
+++ b/Strategy/ObjectCollection.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace DesignPatterns\Strategy;
+
+/**
+ * Class ObjectCollection
+ */
+class ObjectCollection
+{
+    /**
+     * @var array
+     */
+    private $elements;
+
+    /**
+     * @var ComparatorInterface
+     */
+    private $comparator;
+
+    /**
+     * @param array $elements
+     */
+    public function __construct(array $elements = array())
+    {
+        $this->elements = $elements;
+    }
+
+    /**
+     * @return array
+     */
+    public function sort()
+    {
+        $callback = array($this->comparator, 'compare');
+        uasort($this->elements, $callback);
+
+        return $this->elements;
+    }
+
+    /**
+     * @param ComparatorInterface $comparator
+     *
+     * @return void
+     */
+    public function setComparator(ComparatorInterface $comparator)
+    {
+        $this->comparator = $comparator;
+    }
+}
diff --git a/Strategy/Strategy.php b/Strategy/Strategy.php
deleted file mode 100644
index 45187b7..0000000
--- a/Strategy/Strategy.php
+++ /dev/null
@@ -1,111 +0,0 @@
-<?php
-
-namespace DesignPatterns;
-
-/**
- * strategy pattern
- *
- * Terminology:
- * - Context
- * - Strategy
- * - Concrete Strategy
- *
- * Purpose:
- * to separate strategies and to enable fast switching between them.
- * also this pattern is a good alternative to inheritance (instead of having an abstract class that is extended)
- *
- * Examples:
- * - sorting a list of objects, one strategy by date, the other by id
- * - simplify unit testing: e.g. switching between file and in-memory storage
- *
- */
-
-interface Comparator
-{
-    /**
-     * @abstract
-     * @param object $a
-     * @param object $b
-     * @return bool
-     */
-    public function compare($a, $b);
-}
-
-class ObjectCollection
-{
-    private $_elements;
-    private $_comparator;
-
-    /**
-     * @param array $elements
-     */
-    public function __construct(array $elements = array())
-    {
-        $this->_elements = $elements;
-    }
-
-    /**
-     * @return array
-     */
-    public function sort()
-    {
-        $callback = array($this->_comparator, 'compare');
-        uasort($this->_elements, $callback);
-
-        return $this->_elements;
-    }
-
-    /**
-     * @param Comparator $comparator
-     * @return void
-     */
-    public function setComparator(Comparator $comparator)
-    {
-        $this->_comparator = $comparator;
-    }
-}
-
-class IdComparator implements Comparator
-{
-    public function compare($a, $b)
-    {
-        if ($a['id'] == $b['id']) {
-            return 0;
-        } else {
-            return $a['id'] < $b['id'] ? -1 : 1;
-        }
-    }
-}
-
-class DateComparator implements Comparator
-{
-    public function compare($a, $b)
-    {
-        $aDate = strtotime($a['date']);
-        $bDate = strtotime($b['date']);
-
-        if ($aDate == $bDate) {
-            return 0;
-        } else {
-            return $aDate < $bDate ? -1 : 1;
-        }
-    }
-}
-
-$elements = array(
-    array(
-        'id' => 2,
-        'date' => '2011-01-01',
-    ),
-    array(
-        'id' => 1,
-        'date' => '2011-02-01'
-    )
-);
-
-$collection = new ObjectCollection($elements);
-$collection->setComparator(new IdComparator());
-$collection->sort();
-
-$collection->setComparator(new DateComparator());
-$collection->sort();
\ No newline at end of file
diff --git a/Strategy/index.php b/Strategy/index.php
new file mode 100644
index 0000000..d59819a
--- /dev/null
+++ b/Strategy/index.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace DesignPatterns\Strategy;
+
+/**
+ * strategy pattern
+ *
+ * Terminology:
+ * - Context
+ * - Strategy
+ * - Concrete Strategy
+ *
+ * Purpose:
+ * to separate strategies and to enable fast switching between them.
+ * also this pattern is a good alternative to inheritance (instead of having an abstract class that is extended)
+ *
+ * Examples:
+ * - sorting a list of objects, one strategy by date, the other by id
+ * - simplify unit testing: e.g. switching between file and in-memory storage
+ *
+ */
+
+$elements = array(
+    array(
+        'id' => 2,
+        'date' => '2011-01-01',
+    ),
+    array(
+        'id' => 1,
+        'date' => '2011-02-01'
+    )
+);
+
+$collection = new ObjectCollection($elements);
+$collection->setComparator(new IdComparator());
+$collection->sort();
+
+$collection->setComparator(new DateComparator());
+$collection->sort();