显示2-4个小数位（php）

Question

I am trying to figure out a way to produce the following output:

4.0000 = 4.00

4.5000 = 4.50

4.454= 4.454

4.54545454 = 4.5455

4.450 = 4.45

Basically I want to make sure there is ALWAYS at least 2 decimal places and if there are extra zeros, trim to 2 decimal places. If there is more than 4 decimal places round and keep at 4.

I can use:

number_format($number, 4, '.', '');

then rtrim to remove zeros, but this will leave me with less than 2 decimal places in many cases.

Answer 1

function format_number($number) {
    $str = number_format($number, 4, '.', '');
    return preg_replace('/(?<=\d{2})0+$/', '', $str);
}

format_number(4.0)        // "4.00"
format_number(4.5)        // "4.50"
format_number(4.454)      // "4.454"
format_number(4.54545454) // "4.5455"
format_number(4.450)      // "4.45"