Fix php version issue

src/Data/DataSet.php

@@ -436,18 +436,30 @@ public function transform($callback)
 	 *
 	 * @since   3.1.3
 	 */
-	public function filter($callback)
+	public function filter($callback = null)
 	{
 		$dataset = clone $this;
 
-		$dataset->data = array_filter($dataset->data, $callback, ARRAY_FILTER_USE_BOTH);
+		if (!$callback)
+		{
+			$dataset->data = array_filter($dataset->data);
 
-		return $dataset;
-	}
+			return $dataset;
+		}
 
-	public function reject($callback)
-	{
+		$return = array();
 
+		foreach ($dataset->data as $key => $value)
+		{
+			if (call_user_func($callback, $value, $key))
+			{
+				$return[$key] = $value;
+			}
+		}
+
+		$dataset->data = $return;
+
+		return $dataset;
 	}
 
 	/**

src/DataMapper/Test/EntityTest.php

@@ -178,6 +178,13 @@ public function testMutator()
 	 */
 	public function testJsonSerialize()
 	{
+		if (version_compare(PHP_VERSION, '5.4', '<'))
+		{
+			$this->markTestSkipped('PHP 5.3 do not support JsonSerialize()');
+
+			return;
+		}
+
 		$this->assertEquals(json_encode($this->instance->dump(true)), json_encode($this->instance));
 	}
 }