betterCode() PHP 2025

    BcMath\Number::round

    (PHP 8 >= 8.4.0)

    BcMath\Number::round — 任意精度数値を丸める

    説明

    public BcMath\Number::round(int $precision = 0, RoundingMode $mode = RoundingMode::HalfAwayFromZero): BcMath\Number

    $this を、指定した precision(小数点以下の桁数)に丸めた値を返します。 precision を負またはゼロ(デフォルト) とすることも可能です。

    パラメータ

    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
    指定する丸めモード。詳しくは RoundingMode を参照してください。

    戻り値

    結果を新しい BcMath\Number オブジェクトとして返します。

    エラー / 例外

    このメソッドは、無効な mode が指定された場合に ValueError をスローします。

    例

    例1 BcMath\Number::round() の例

    <?php
    var_dump    (
    new     BcMath\Number('3.4')->round(),
    new     BcMath\Number('3.5')->round(),
    new     BcMath\Number('3.6')->round(),
    new     BcMath\Number('3.6')->round(0),
    new     BcMath\Number('5.045')->round(2),
    new     BcMath\Number('5.055')->round(2),
    new     BcMath\Number('345')->round(-2),
    new     BcMath\Number('345')->round(-3),
    new     BcMath\Number('678')->round(-2),
    new     BcMath\Number('678')->round(-3),
    );
    ?>

    上の例の出力は以下となります。

    object(BcMath\Number)#2 (2) {
  ["value"]=>
  string(1) "3"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(4) "5.05"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(4) "5.06"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(3) "300"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "0"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#10 (2) {
  ["value"]=>
  string(3) "700"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(4) "1000"
  ["scale"]=>
  int(0)
}

    例2 BcMath\Number::round() で異なる precision を指定した例

    <?php
    $number     = new BcMath\Number('123.45');

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

    上の例の出力は以下となります。

    object(BcMath\Number)#2 (2) {
  ["value"]=>
  string(7) "123.450"
  ["scale"]=>
  int(3)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(6) "123.45"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(5) "123.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(3) "123"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(3) "120"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(3) "100"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(1) "0"
  ["scale"]=>
  int(0)
}

    例3 BcMath\Number::round() で異なる mode を指定した例

    <?php
    echo 'Rounding modes with 9.5' . PHP_EOL;
    $number = new BcMath\Number('9.5');
    var_dump(
    $number->round(0, RoundingMode::HalfAwayFromZero),
    $number->round(0, RoundingMode::HalfTowardsZero),
    $number->round(0, RoundingMode::HalfEven),
    $number->round(0, RoundingMode::HalfOdd),
    $number->round(0, RoundingMode::TowardsZero),
    $number->round(0, RoundingMode::AwayFromZero),
    $number->round(0, RoundingMode::NegativeInfinity),
    $number->round(0, RoundingMode::PositiveInfinity),
    );

    echo     PHP_EOL;
    echo     'Rounding modes with 8.5' . PHP_EOL;
    $number = new BcMath\Number('8.5');
    var_dump(
    $number->round(0, RoundingMode::HalfAwayFromZero),
    $number->round(0, RoundingMode::HalfTowardsZero),
    $number->round(0, RoundingMode::HalfEven),
    $number->round(0, RoundingMode::HalfOdd),
    $number->round(0, RoundingMode::TowardsZero),
    $number->round(0, RoundingMode::AwayFromZero),
    $number->round(0, RoundingMode::NegativeInfinity),
    $number->round(0, RoundingMode::PositiveInfinity),
    );
    ?>

    上の例の出力は以下となります。

    Rounding modes with 9.5
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#13 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#15 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#17 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}

Rounding modes with 8.5
object(BcMath\Number)#1 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#15 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#13 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}

    例4 BcMath\Number::round() で precision を指定し、 異なる mode を指定した例

    <?php
    $positive     = new BcMath\Number('1.55');
    $negative = new BcMath\Number('-1.55');

    echo     'Using RoundingMode::HalfAwayFromZero with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::HalfAwayFromZero),
    $negative->round(1, RoundingMode::HalfAwayFromZero),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::HalfTowardsZero with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::HalfTowardsZero),
    $negative->round(1, RoundingMode::HalfTowardsZero),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::HalfEven with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::HalfEven),
    $negative->round(1, RoundingMode::HalfEven),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::HalfOdd with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::HalfOdd),
    $negative->round(1, RoundingMode::HalfOdd),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::TowardsZero with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::TowardsZero),
    $negative->round(1, RoundingMode::TowardsZero),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::AwayFromZero with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::AwayFromZero),
    $negative->round(1, RoundingMode::AwayFromZero),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::NegativeInfinity with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::NegativeInfinity),
    $negative->round(1, RoundingMode::NegativeInfinity),
    );

    echo     PHP_EOL;
    echo     'Using RoundingMode::PositiveInfinity with 1 decimal digit precision' . PHP_EOL;
    var_dump(
    $positive->round(1, RoundingMode::PositiveInfinity),
    $negative->round(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
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfTowardsZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfEven with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfOdd with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::TowardsZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::AwayFromZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#10 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::NegativeInfinity with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::PositiveInfinity with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#12 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

    参考

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