Depends on exactly what you are trying to achieve here....
$number = "14567.4567";
$english_format_number = number_format($number, 2, '.', '');
echo $english_format_number;
// Outputs 14567.46
Or, if you are just trying to round the number, you might look at the [man]round()[/man] function instead.
$number = "14567.4567";
$english_format_number = round($number, 2);
echo $english_format_number;
// Outputs 14567.46