<?php
class Math {
  private static $count = 0;
  public function __construct() {
    self::$count++;
  }
  public static function calcSin($x) {
    return sin($x);
  }
  public static function calcSQRT($x) {
    return sqrt($x);
  }
  public static function getCount() {
    return self::$count;
  }
}
echo Math::calcSin(1);
echo "<br />";
echo Math::calcSQRT(9);
echo "<br />";
$math = new Math();
$math_2 = new Math();
echo Math::getCount();
?>