"Irfan Khan", "Irrfan Khan" and "Irrfan" are all the same person and is known as "Irrfan Khan".
Also "Kadar Khan" and "Kader Khan" are the same person and he's known as "Kader Khan".
Again "Salmaan Khan" and "Salman Khan" are the same person and he's known as "Salman Khan".
Thanks.