Fixed a Serializer example

Author: javiereguiluz

components/serializer.rst

@@ -843,9 +843,10 @@ Option                  Description                                           De
 ``csv_key_separator``   Sets the separator for array's keys during its        ``.``
                         flattening
 ``csv_headers``         Sets the order of the header and data columns
-                        E.g.: ``serialize(['c' => 3,'a' => 1,'b' => 2],
-                        'csv', ['csv_headers' => ['a', 'b', 'c']]);``
-                        returns ``a,b,c\n1,2,3 ``                             ``[]``, inferred from input data's keys
+                        E.g.: if ``$data = ['c' => 3, 'a' => 1, 'b' => 2]``
+                        and ``$options = ['csv_headers' => ['a', 'b', 'c']]``
+                        then ``serialize($data, 'csv', $options)`` returns
+                        ``a,b,c\n1,2,3 ``                                     ``[]``, inferred from input data's keys
 ``csv_escape_formulas`` Escapes fields containg formulas by prepending them   ``false``
                         with a ``\t`` character
 ``as_collection``       Always returns results as a collection, even if only