替换数组函数中的值/键

Question

I am looking for function which will replace array keys, for example:

change this array:

array(0 => a, 1 => b, 2 => c)

to:

array(0 => a, 1 => c, 2 => b)

so i have array keys 0,1,2 and their values, and i want to change value of key 1and replace it with value from key 2, i hope i was cleare, thanks