Update reference/pdo/pdostatement/fetch.xml

Co-authored-by: Kamil Tekiela <[email protected]>

reference/pdo/pdostatement/fetch.xml

@@ -271,7 +271,7 @@ Reading backwards:
 
    <example><title>Construction order</title>
     <simpara>
-     When objects are fetched via <class>PDO::FETCH_CLASS</class>, the object
+     When objects are fetched via <constant>PDO::FETCH_CLASS</constant>, the object
      properties are assigned first, and then the constructor of the class is
      invoked. However, when <constant>PDO::FETCH_PROPS_LATE</constant> is also given,
      this order is reversed, i.e. first the constructor is called, and