PHP Maths Logic

Question

I am trying to set a variable based on some maths logic (to wrap specific html around elements).

I worked half the problem, to hit 0, 3, 6, 9, 12

if(($i % 3) == 0) { // blah }

Now I need to hit the following numbers, 2, 5, 8, 11, 14, etc

What possible maths operation could I do to hit this sequence?

Answer 1

if($i % 3 == 1)
if($i % 3 == 2)

Modulo returns the remainder, so when you match the 0, you get the 3rd, 6th, 9th, etc, because 0 is left in the division.

So just check for when 1 remains and 2 remains.

Answer 2

if((($i-2) % 3) == 0) { // blah }

Answer 3

Along with Tor Valamo's answer you can notice the pattern of (3 * $i) - 1

(3*1)-1 = 2
(3*2)-1 = 5
(3*3)-1 = 8
   ...