Function Bulatkan Angka (Statis)

<?php
$angka = 8161824.6;
$potong1 = substr($angka, 0, 3);
$potong2 = ceil(substr($angka, 3, strlen($angka)));
$bulat = substr($potong2, 1, 1);
$bulat1 = substr($potong2, 0, 1);
$bulat2 = $bulat>=5?$bulat1+1:$bulat1;
$nol = "";
for ($i = 0;$i < strlen($potong2)-1;$i++) {
    $nol .= "0";
}
echo $potong1.$bulat2.$nol;
?>