number_format() returns a formatted version of
number. This function accepts either one,
two or four parameters (not three):
If only one parameter is given,
number will be formatted without decimals,
but with a comma (",") between every group of thousands.
If two parameters are given, number will
be formatted with decimals decimals with a
dot (".") in front, and a comma (",") between every group of
thousands.
If all four parameters are given, number
will be formatted with decimals decimals,
dec_point instead of a dot (".") before
the decimals and thousands_sep instead of
a comma (",") between every group of thousands.
Only the first character of thousands_sep
is used. For example, if you use bar as
thousands_sep on the number
1000, number_format() will
return 1b000.
See also: money_format(), sprintf(), printf() and sscanf().