Question

I have this code:

$um = array("PHP", "JAVA", "MySQL")


 $a = count($um)

       for ($i = 0; $i < $a; $i++) {
            for ($x = $i + 1; $x <$a; $x++) {
                $arr1 [] = array($um[$i],$um[$x]);
            }
        }

This will output something like these combinations:

PHP[0] JAVA[1]
PHP[0] MySQL[2]
JAVA[1] MySQL[2]

Well, works without any problem.

But now, i want to change the output to something like:

PHP[0] JAVA[1]
JAVA[1] MySQL[2]
MySQL[2] PHP[0]

The logic will be the same for the three array elements or even 10, and so on.

Any idea about this ?

Answer 1

Just use modular arithmetic: you want to pair indices (i,i+1), where the i+1 wraps around to 0 if it becomes too large.

for ($i = 0; $i < $a; $i++) {
    echo $um[$i], ', ', $um[($i+1) % $a]
}

So for $a=3 this displays according to indices:

0, 1
1, 2
2, 0 (since 3 % 3==0)

Modulus Operator docs