html transformations

Hi, I want to write a parser over the docbook html output to highlight the php code in the pear manual. My problem is that now the docbook tag: <programlisting role="php"> is converted to only: <PRE CLASS="programlisting"> with not difference between one language and an another. How can I (or start looking at) convert the role="php" to something like <PRE CLASS="programphp">? Thanks, Tomas V.V.Cox PS.- Please CC me also if you reply to this msg, I'm not suscribed to this list.