how to get aeris back

i dont know how to get aeris back after she dies... can someone inlighten me? ive heard theres a way but i dont know how.

Cheat codes. That's the only way. Well done for not saying 'lol'.

ty ET im working on it heh... well.. how do you do it without the cheatcodes... ive seen someone with aerith.. but they wouldn't tell me how to get her >.<