php round off value with trailing 2 decimals and multiples of 5

Question

I tried this function

function roundUpToAny($n,$x=5) {
    return (round($n)%$x === 0) ? round($n) : round(($n+$x/2)/$x)*$x;
}

echo roundUpToAny(4.52); // This show 5 instead of 4.55

echo roundUpToAny(5.1); // This show 5 instead of 5.10

How can i created such function

This question is about rounding - it may be useful: [4483540/php-show-a-number-to-2-decimal-places](http://stackoverflow.com/questions/4483540/php-show-a-number-to-2-decimal-places) — Ryan Vincent, May 24 '14 at 02:16
Multiply by two, round to 1 sf, divide by two. Does it have to work for negative numbers? — Floris, May 24 '14 at 02:17
@RyanVincent I tried the one in the link provied, If my input is 4.21 its giving 4.21 as output instead of 4.25 — Prabhakaran, May 24 '14 at 02:25

Floris · Accepted Answer · 2014-06-02T14:23:36.353

I think the following function does what you want:

function roundUpToAny($n, $x=5, $sf=2) {
  $scale = pow(10,$sf);
  return number_format(round(ceil($n*$scale / $x), $sf) * $x / $scale, $sf);
}

The first argument is the number to be converted, the second is the "rounding factor" (multiples of $x - you asked for 5 in the title of the question), the third is the number of figures after the decimal point.

Test:

echo roundUpToAny(1.23, 5, 2) ."\n";
echo roundUpToAny(4.54, 5, 2) ."\n";
echo roundUpToAny(5.101, 5, 3) ."\n";
echo roundUpToAny(1.19, 5, 3) ."\n";

Result:

UPDATE

You pointed out in a follow-up that the above code fails for inputs of 1.1 and 2.2. The reason for this is the fact that these numbers are not exactly representable in double precision (strange though this may sound). The following code compensates for this, by creating an intermediate value that is rounded to be an integer (and therefore can be represented exactly):

function roundUpToAny($n, $x=5, $sf=2) {
  $scale = pow(10,$sf);
  $temp = round($n * $scale, $sf); // get rid of small rounding errors
  return number_format(round(ceil($temp / $x), $sf) * $x / $scale, $sf);
}

Testing:

echo roundUpToAny(1.1, 5, 2) ."\n";

Result:

1.10

As expected.

almost ok but `roundUpToAny(1.23, 5, 2)` this results 1.2 instead 1.20 — Prabhakaran, May 24 '14 at 02:37
The function returns a value. Do you need it to return a string? Anyway - `roundUpToAny(1.23, 5, 2)` returns 1.25 for me... — Floris, May 24 '14 at 02:37
Hi I am facing one problem with above function can you clear it — Prabhakaran, Jun 02 '14 at 08:44

php round off value with trailing 2 decimals and multiples of 5

1 Answers1