title: If a number is multiple of 3 starting at different numbers
body: <p>I'm not sure of the mathematical term for what I'm after, but I'm looking for a way in PHP to assign a variable to an integer which is a multiple of three. The multiple will start from numbers 1, 2 and 3. All integers will fall under one of three variables <code>$varA</code>, <code>$varB</code> and <code>$varC</code>. I think the modulus operator should be used, but I'm not sure how.</p>
  
  <p><code>$varA</code> could include numbers 1, 4, 7, 10, 13, 16, 19 etc.<br>
  <code>$varB</code> could include numbers 2, 5, 8, 11, 14, 17, 20 etc.<br>
  <code>$varC</code> could include numbers 3, 6, 9, 12, 15, 18, 21 etc.</p>
  
  <p>I want to assign the number from an if statement, such as:</p>
  
  <pre><code>if( $number == (test for $varA) ) {
      $number = $varA
  } else if( $number == (test for $varB) ) {
      $number = $varB
  } else {
      $number = $varC
  }
  </code></pre>