What setting do I need to find to fix this?

What setting do I need to find to fix this?

I'm running the same code on two different servers and I'm getting a
different result. I'm not sure what I need to change to fix this.
I'm working with a timestamp and I'm using the following.
$timestamp = round(microtime(true) * 1000);
echo $timestamp;
When I do that from my local test server running PHP 5.4.16 I get a value
like: 1376732353181
When I run the same thing from my live server running PHP 5.3.6 I a value
like: 1.37673257778E+12
I need my live server to act the same way as my test server and I'm not
sure what's causing the difference.
The problem seems to occur at the point of multiplying by 1000 and getting
a large number. My local server gives me a regular number back while the
other server gives me a decimal with E+12 on the end. I forgot what that's
called..?? I don't want it, though.
Any information on this would be greatly appreciated. Thanks!