PHPerKaigi 2025

    BcMath\Number::round

    (PHP 8 >= 8.4.0)

    BcMath\Number::round — Rounds an arbitrary precision number

    说明

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

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

    参数

    precision

    可选的十进制小数点后数字的数目。

    如果 precision 是正数，则 num 会四舍五入到小数点后 precision 位有效数字。

    如果 precision 是负数，则 num 四舍五入到小数点前 precision 位有效数字。即 pow(10, -$precision) 最接近的倍数，例如，precision 为 -1，num 可以四舍五入到十位，precision 为 -2，num 可以四舍五入到百位，等等。

    mode
    Specifies the rounding mode.

    返回值

    Returns the result as a new BcMath\Number object.

    示例

    示例 #1 BcMath\Number::round() example

    <?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),
    );
    ?>

    以上示例会输出：

    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)
}

    示例 #2 Example of using BcMath\Number::round() with different precision values

    <?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),
    );
    ?>

    以上示例会输出：

    object(BcMath\Number)#2 (2) {
  ["value"]=>
  string(6) "123.45"
  ["scale"]=>
  int(2)
}
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)
}

    示例 #3 Example of using BcMath\Number::round() with different mode values

    <?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),
    );
    ?>

    以上示例会输出：

    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)
}

    示例 #4 Example of using BcMath\Number::round() with different mode values when specifying precision

    <?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),
    );
    ?>

    以上示例会输出：

    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)
}

    参见

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