title: Apply class to numbers belonging to a sequence php photo grid
body: <p>I' trying to apply a class third item in a row in a php photo grid output.</p>
  
  <p>For instance </p>
  
  <pre><code>0 1 2
  3 4 5
  6 7 8
  9 10 11
  </code></pre>
  
  <p>i would want to apply a class to the number 2, 5, 8, 11 and so on... </p>
  
  <p>If the variable $i stores the number how can I check with php to see if it is part of that sequence using an if statement</p>