PHP if is a multiple of an integer

Question

Within a for loop, i need to add some HTML that outputs only when the loop is on a [(multiple of 3) minus 1].

For example, what i could do is:

for($i=0;          


        

Answer 1

if ( $i==0 || ($i+1)%3 == 0 )
{
    //do stuff
}

What this will do, is go to the next index, divide it by 3, and see if there is a remainder. If there is none, then that means that the current index is one less than a number that is divisible by 3