<?
$a = microtime(true);
$d = array(2,3,5,7);
for ($b = 11;$b < 1000;$b += 2) {
  if (($b % 3) && ($b % 5) && ($b % 7)) {
    $e = true;
    if ($b > 49) {
      $f = sqrt($b);
      for ($c = 4;$g = $d[$c],$g <= $f;$c++) {
        if (!($b % $g)) {
          $e = false;
          break;
        }
      }
    }
    if ($e) $d[] = $b;
  }
}
printf("%01.5f",microtime(true)-$a);
print_r($d);
?>