BC Math 関数
PHP マニュアル

bcround

Round arbitrary precision number

説明

string bcround(string $num, int $precision = 0, RoundingMode $mode = RoundingMode::HalfAwayFromZero)

Returns the rounded value of num to specified precision (number of digits after the decimal point). precision can also be negative or zero (default).

パラメータ

num

丸める値。

precision

オプションで指定する、丸める桁数。

precision が正の値の場合、 num は 小数点以下、有効桁数 precision 桁に丸められます。

precision が負の場合、 num の 丸め処理は小数点より前の precision 桁に対して行われます。 つまり、一番近い pow(10, -$precision) の倍数に丸められます。 たとえば、precision が -1 の場合、 num は 一番近い10の倍数に、 precision が -2 の場合は 一番近い100の倍数に丸められる、という具合です。

mode
Specifies the rounding mode.

戻り値

Returns a numeric string representing num rounded to the given precision.

エラー / 例外

This function throws a ValueError in the following cases:

  • num is not a well-formed BCMath numeric string.
  • scale is outside the valid range.

例

例1 bcround examples

<?php
var_dump(bcround('3.4'));
var_dump(bcround('3.5'));
var_dump(bcround('3.6'));
var_dump(bcround('3.6', 0));
var_dump(bcround('5.045', 2));
var_dump(bcround('5.055', 2));
var_dump(bcround('345', -2));
var_dump(bcround('345', -3));
var_dump(bcround('678', -2));
var_dump(bcround('678', -3));
?>

上の例の出力は以下となります。

string(1) "3"
string(1) "4"
string(1) "4"
string(1) "4"
string(4) "5.05"
string(4) "5.06"
string(3) "300"
string(1) "0"
string(3) "700"
string(4) "1000"

例2 Example of using bcround with different precision values 

<?php
$number = '123.45';

var_dump(bcround($number, 3));
var_dump(bcround($number, 2));
var_dump(bcround($number, 1));
var_dump(bcround($number, 0));
var_dump(bcround($number, -1));
var_dump(bcround($number, -2));
var_dump(bcround($number, -3));
?>

上の例の出力は以下となります。

string(7) "123.450"
string(6) "123.45"
string(5) "123.5"
string(3) "123"
string(3) "120"
string(3) "100"
string(1) "0"

例3 Example of using bcround with different mode values 

<?php
echo 'Rounding modes with 9.5' . PHP_EOL;
var_dump(bcround('9.5', 0, RoundingMode::HalfAwayFromZero));
var_dump(bcround('9.5', 0, RoundingMode::HalfTowardsZero));
var_dump(bcround('9.5', 0, RoundingMode::HalfEven));
var_dump(bcround('9.5', 0, RoundingMode::HalfOdd));
var_dump(bcround('9.5', 0, RoundingMode::TowardsZero));
var_dump(bcround('9.5', 0, RoundingMode::AwayFromZero));
var_dump(bcround('9.5', 0, RoundingMode::NegativeInfinity));
var_dump(bcround('9.5', 0, RoundingMode::PositiveInfinity));

echo PHP_EOL;
echo 'Rounding modes with 8.5' . PHP_EOL;
var_dump(bcround('8.5', 0, RoundingMode::HalfAwayFromZero));
var_dump(bcround('8.5', 0, RoundingMode::HalfTowardsZero));
var_dump(bcround('8.5', 0, RoundingMode::HalfEven));
var_dump(bcround('8.5', 0, RoundingMode::HalfOdd));
var_dump(bcround('8.5', 0, RoundingMode::TowardsZero));
var_dump(bcround('8.5', 0, RoundingMode::AwayFromZero));
var_dump(bcround('8.5', 0, RoundingMode::NegativeInfinity));
var_dump(bcround('8.5', 0, RoundingMode::PositiveInfinity));
?>

上の例の出力は以下となります。

Rounding modes with 9.5
string(2) "10"
string(1) "9"
string(2) "10"
string(1) "9"
string(1) "9"
string(2) "10"
string(1) "9"
string(2) "10"

Rounding modes with 8.5
string(1) "9"
string(1) "8"
string(1) "8"
string(1) "9"
string(1) "8"
string(1) "9"
string(1) "8"
string(1) "9"

例4 Example of using bcround with different mode values when specifying precision 

<?php
echo 'Using RoundingMode::HalfAwayFromZero with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::HalfAwayFromZero));
var_dump(bcround(-1.55, 1, RoundingMode::HalfAwayFromZero));

echo PHP_EOL;
echo 'Using RoundingMode::HalfTowardsZero with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::HalfTowardsZero));
var_dump(bcround(-1.55, 1, RoundingMode::HalfTowardsZero));

echo PHP_EOL;
echo 'Using RoundingMode::HalfEven with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::HalfEven));
var_dump(bcround(-1.55, 1, RoundingMode::HalfEven));

echo PHP_EOL;
echo 'Using RoundingMode::HalfOdd with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::HalfOdd));
var_dump(bcround(-1.55, 1, RoundingMode::HalfOdd));

echo PHP_EOL;
echo 'Using RoundingMode::TowardsZero with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::TowardsZero));
var_dump(bcround(-1.55, 1, RoundingMode::TowardsZero));

echo PHP_EOL;
echo 'Using RoundingMode::AwayFromZero with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::AwayFromZero));
var_dump(bcround(-1.55, 1, RoundingMode::AwayFromZero));

echo PHP_EOL;
echo 'Using RoundingMode::NegativeInfinity with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::NegativeInfinity));
var_dump(bcround(-1.55, 1, RoundingMode::NegativeInfinity));

echo PHP_EOL;
echo 'Using RoundingMode::PositiveInfinity with 1 decimal digit precision' . PHP_EOL;
var_dump(bcround( 1.55, 1, RoundingMode::PositiveInfinity));
var_dump(bcround(-1.55, 1, RoundingMode::PositiveInfinity));
?>

上の例の出力は以下となります。

Using RoundingMode::HalfAwayFromZero with 1 decimal digit precision
string(3) "1.6"
string(4) "-1.6"

Using RoundingMode::HalfTowardsZero with 1 decimal digit precision
string(3) "1.5"
string(4) "-1.5"

Using RoundingMode::HalfEven with 1 decimal digit precision
string(3) "1.6"
string(4) "-1.6"

Using RoundingMode::HalfOdd with 1 decimal digit precision
string(3) "1.5"
string(4) "-1.5"

Using RoundingMode::TowardsZero with 1 decimal digit precision
string(3) "1.5"
string(4) "-1.5"

Using RoundingMode::AwayFromZero with 1 decimal digit precision
string(3) "1.6"
string(4) "-1.6"

Using RoundingMode::NegativeInfinity with 1 decimal digit precision
string(3) "1.5"
string(4) "-1.6"

Using RoundingMode::PositiveInfinity with 1 decimal digit precision
string(3) "1.6"
string(4) "-1.5"

参考

  • bcceil
  • bcfloor