将$ 516.91兑换成51691

I have an input: 516.91. I need to convert it to 51691.

I write a small test code but it doesn't work.

Some examples:

56    -> 5600
56.1  -> 5610
56.13 -> 5613
100   -> 10000

How to convert 516.91 to 51691 with PHP ?

<?php

$varA = 516.91;                                   

$varB = intval(floatval($varA)*1000/10);


$shouldBe = 51691;


if ($varB == $shouldBe) {
    echo "OK";
} else {
    echo "NOK - " . $varB . " != " . $shouldBe;
}

Ok .. I found ... bcmul and it work