如何获得连续3的第二项？

Question

I have a webpage layout where there are rows of 3. I need to gove the middle item a special css class. How to do that?

div [div] div
div [div] div
div [div] div
div [div] div

I know with table rows you can get alternating row colors using the ternary operator to detect them:

class="<?= $key % 2 == 0 ? 'odd' : 'even'"

but how to do it for the 2nd in a row of 3?

P.S. I am awful at math, perhaps the answer is quite obvious.

Answer 1

Modify the divisor for the modulus test to 3 (for every block of 3 rows); and test for a result of 1 (the 2nd entry from offset 0)

class="<?= $key % 3 == 1 ? 'odd' : 'even'"