And what are you trying to achieve with PHP or C#? People usually use Javascript in reports, but if you want to use other languages like PHP, you can try out Cognos Mashup Services. http://www.ibm.com/developerworks/data/library/techarticle/dm-1001cognosmashup/
Be aware, you need to have an SDK license to use it (at least needed the last time I check). Maybe worth running this through IBM rep.