Every country has a different way of displaying numbers and currencies, even if you will be displaying the same number.

localeconv()
The localconv() function will give you all necessary information about the current locale.

<?php
$c 
localeconv();
var_dump($c);
?>
number_format()
The number_format() function along with localeconv() will allow you to get locale specific information.

<?php
$linfo 
localeconv();

function 
locale_num ($n
{
    global 
$linfo;

    return 
number_format($n
                         
$linfo['decimal_point'], 
                         
$linfo['thousands_sep']);
}

print 
locale_num(100);
print 
locale_num(200203002);
print 
locale_num(139939.23321);
?>