检查数字的因素

I'm not sure if this title is correct but here's basically what I am trying to do.

I am trying to check if a number is less than 100 and if it isn't I would like to know what factor of 10 I need to divide it by to get below 100 i.e. for 7923 the factor is 100 to make it 79.23 and for 452,936,489 the factor would be 10,000,000 to make it 45.2936489.

Is there a function or a piece of script that does that out there?

Cheers

$number = 452936489;
$factor = pow(10, ceil(log($number/100) / log(10)));

Ok. basic math:

you need to find a power of 10 divisor that reduces your number below 100, so the log business figures out the exact fractional power of 10 required to turn 10 into your original number. That comes out to be around 6.6560373....

That gets rounded up to 7, and is then used to raise 10 to that power.

10^7 = 10,000,000
452936489 / 10^7 = 45.2936489

<?
$num = 7923;
$x = 10;
while(true)
{
    $result = $num/$x;
    if($result < 100) 
    {
        die($x.""); 
    }
    else
    {
        $x *= 10;
    }
}
?>