Round to Highest Factor with Variable Scale?

Question

PHP's floor() and ceil() is useful for rounding floats to their nearest integers.

But what if we need to find the highest multiple of 10 (hundreds, thousands, etc.) for a given number? For example:

num_to_scale(538.9)           // 500
num_to_scale(543123654.01234) // 5000000

Answer 1

function num_to_scale($number) {
  $multiple=1; $test=1;
  for ($i=1; $test>=1; $i++) {
    $factor = $multiple/10;
    $test = $number/$multiple;
    $multiple = $multiple*10;
    $scale = floor($number/$factor)*$factor;
  } return $scale;
}

or more simply:

function num_to_scale($n) {
  $m=1; $t=1;
  for ($i=1; $t>=1; $i++) {
    $f=$m/10; $t=$n/$m; $m=$m*10; $s=floor($n/$f)*$f;
  } return $s;
}

Combined with a helper function to convert integers to text strings, we can easily do something like this:

echo 'Over '.num_to_scale(5395206).' units sold.';
// Over five million units sold.

Answer 2

try this:

function num_to_scale($number) {
    $num = (int) floor($number);
    $ln = strlen($num) - 1;

    return (int) floor($num / pow(10, $ln)) * pow(10, $ln);
}

Answer 3

Try this code, check the live demo. You also can refer to this post.

  $floor = floor($v);
  return str_pad(substr($floor, 0, 1), strlen($floor), '0');

Answer 4

My answer uses logarithm :

function num_to_scale($var) {
    $nbDigits = (int)log($var,10);
    return (int)($var/10**$nbDigits)*10**$nbDigits;
}