latte filter number and php function number

Hi

i have a special problem with formating number.

if i use number filter in template

{var $number = -0.34123}
{$number|number:2:',':' '}

output is: –0.35

and then if i use number() function

<?php number(-0.34123,2,',',' '); ?>

output is –0.34

How is it possible ?? Thanks for help