Eratostenes Sieve

sieve.php

<?php

function eratostenes_sieve($number) {
    $num_max = floor(sqrt($number));
    $list    = range(2, $number);

    for($x = 2; $x <= $num_max; $x++) {
        foreach($list as $_k => $_val) {
            if($_val != $x and $_val % $x == 0) {
                unset($list[$_k]);
            }
        }
    }

    sort($list);
    return $list;
}