title: Why the Functions aren't defined ? PHP
body: <p>What do I have to do so that I can use the standard php functions without creating an instance of a Math_functions Class ?</p>
  
  <pre><code>&lt;?php
  
      class Math_functions {
  
          public static function evenNumber($number) {
              return !($number &amp; 1);
          }
  
          public static function natual_sum($n) {
              while ($n) {
                  if (evenNumber($n)) {
                      $sum = $sum + $n;
                  }
                  $n--;
              }
              return $sum;
          }
  
      }
  
      echo natual_sum(4);
  ?&gt;
  </code></pre>