define $instance and make the example more clear

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@294876 c90b9560-bf6c-de11-be94-00142212c4b1

language/oop5/basic.xml

@@ -149,6 +149,9 @@ $instance = new $className(); // Foo()
     <programlisting role="php">
 <![CDATA[
 <?php
+
+$instance = new SimpleClass();
+
 $assigned   =  $instance;
 $reference  =& $instance;