<?php function is_prime($prime) { $sqrt = sqrt($prime); for ($i = 3; $i <= $sqrt; $i+=2){ if ($prime%$i == 0) return false; } return true; } $sum = 2+3; for($number = 5; $number < 2000000; $number+=2) { if (is_prime($number)) { $sum += $number; } } echo $sum;