array_rand() is rather useful when you want to
pick one or more random entries out of an array.
Parameters
input
The input array.
num_req
Specifies how many entries you want to pick - if not specified,
defaults to 1.
Return Values
If you are picking only one entry, array_rand()
returns the key for a random entry. Otherwise, it returns an array
of keys for the random entries. This is done so that you can pick
random keys as well as values out of the array.