2.10.3. Discussion
The number_format( ) function formats a number by
inserting the correct decimal and thousands separators for your
locale. If you want to manually specify these values, pass them as
the third and fourth parameters:
$number = 1234.56;
print number_format($number, 2, '@', '#'); // 1#234@56
The third argument is used as the decimal point and the last
separates thousands. If you use these options, you must specify both
arguments.
By default, number_format( ) rounds the number to
the nearest integer. If you want to preserve the entire number, but
you don't know ahead of time how many digits follow
the decimal point in your number, use this:
$number = 1234.56; // your number
list($int, $dec) = explode('.', $number);
print number_format($number, strlen($dec));