function isPrime($n) {
if ($n < 2 || ($n % 2 == 0 && $n != 2)) {
return 0;
}
$count = floor(sqrt($n));
for ($i = 3; $i <= $count; $i += 2) {
if ($n % $i == 0) {
return 0;
}
}
return 1;
}
for ($n = 2; $n <= 100; $n++) {
if (isPrime($n)) {
echo $n . " ";
}
}
/*
run:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
*/