PHP: ceil() and floor() with precision

ceil_floor_with_precision.php

<?php

function ceil_plus(float $value, ?int $precision = null): float
{
  if (null === $precision) {
    return (float) ceil($value);
  }
  if ($precision < 0) {
    throw new \RuntimeException('Invalid precision');
  }

  $reg = $value + 0.5 / (10 ** $precision);
  return round($reg, $precision, $reg > 0 ? PHP_ROUND_HALF_DOWN : PHP_ROUND_HALF_UP);
}

function floor_plus(float $value, ?int $precision = null): float
{
  if (null === $precision) {
    return (float)floor($value);
  }
  if ($precision < 0) {
    throw new \RuntimeException('Invalid precision');
  }

  $reg = $value - 0.5 / (10 ** $precision);
  return round($reg, $precision, $reg > 0 ? PHP_ROUND_HALF_UP : PHP_ROUND_HALF_DOWN);
}

// Tests for ceil_plus().
assert(ceil_plus(3.14, 0) === 4.0);
assert(ceil_plus(3.14, 1) === 3.2);
assert(ceil_plus(3.14, 2) === 3.14);
assert(ceil_plus(3.1415, 0) === 4.0);
assert(ceil_plus(3.1415, 1) === 3.2);
assert(ceil_plus(3.1415, 2) === 3.15);
assert(ceil_plus(3.1415, 3) === 3.142);
assert(ceil_plus(3.1415, 4) === 3.1415);

assert(ceil_plus(0.002, 3) === 0.002);
assert(ceil_plus(0.0015, 3) === 0.002);
assert(ceil_plus(0.001, 3) === 0.001);
assert(ceil_plus(0, 0) === 0.0);
assert(ceil_plus(-0.001, 3) === -0.001);
assert(ceil_plus(-0.0015, 3) === -0.001);
assert(ceil_plus(-0.002, 3) === -0.002);
assert(ceil_plus(-1, 0) === -1.0);

// Tests for floor_plus().
assert(floor_plus(3.14, 0) === 3.0);
assert(floor_plus(3.14, 1) === 3.1);
assert(floor_plus(3.14, 2) === 3.14);
assert(floor_plus(3.1415, 0) === 3.0);
assert(floor_plus(3.1415, 1) === 3.1);
assert(floor_plus(3.1415, 2) === 3.14);
assert(floor_plus(3.1415, 3) === 3.141);
assert(floor_plus(3.1415, 4) === 3.1415);

assert(floor_plus(0.002, 3) === 0.002);
assert(floor_plus(0.0015, 3) === 0.001);
assert(floor_plus(0.001, 3) === 0.001);
assert(floor_plus(0, 0) === 0.0);
assert(floor_plus(-0.001, 3) === -0.001);
assert(floor_plus(-0.0015, 3) === -0.002);
assert(floor_plus(-0.002, 3) === -0.002);
assert(floor_plus(-1, 0) === -1.0);

@malsatin Thank you for your comments. Your code looks better. I'd like to update the code but I'm busy and don't have enough time now... :( I'll come back soon. Thanks!

@malsatin Sorry for my slow reaction. I tested some cases with you implementation and they look fine! I've updated the code above with some additional assertions. Thank you.

Thank you too. Hopefully this thread would help someone in the future