<?php for ($i = 2; $i <= 20; $i++) { for ($j = 2; $j*$j <= $i; $j++) if ($i % $j == 0) continue 2; $prime[] = $i; }
Standard input is empty
array(8) {
[0]=>
int(2)
[1]=>
int(3)
[2]=>
int(5)
[3]=>
int(7)
[4]=>
int(11)
[5]=>
int(13)
[6]=>
int(17)
[7]=>
int(19)
}