Question

Here is an array.

$item = array('A', 'B', 'C', 'D');

I want to list all possible orders in this array like:

A

A,B

A,B,C

A,B,C,D

A,C

A,C,D

A,C,B

…

B,A

B,A,C

….

How can I do that?

Answer 1

The permutations you want to know can be accomplished through this algorithm and applying in a loop for the subsets.

Initialize the first permutation with <1 <2 …

while there exists a mobile integer

find the largest mobile integer k

swap k and the adjacent integer it is looking at

reverse the direction of all integers larger than k

Refer to this question for more info