PHP Conference Japan 2024

    bcround

    (PHP 8 >= 8.4.0)

    bcround — 对任意精度数字进行四舍五入

    描述

    bcround(字符串 $num, 整数 $precision = 0, RoundingMode $mode = RoundingMode::HalfAwayFromZero): 字符串

    返回num四舍五入到指定precision（小数点后位数）的值。precision也可以是负数或零（默认值）。

    参数

    num

    要四舍五入的值。

    precision

    可选的小数位数，用于四舍五入。

    如果precision为正数，则num将四舍五入到小数点后precision位有效数字。

    如果precision为负数，则num将四舍五入到小数点前precision位有效数字，即四舍五入到pow(10, -$precision)的最近倍数，例如，对于precision为-1，num将四舍五入到十位数，对于precision为-2，则四舍五入到百位数，等等。

    mode
    指定舍入模式。

    返回值

    返回一个数值字符串，表示num四舍五入到给定精度后的值。

    错误/异常

    此函数在以下情况下会抛出ValueError异常

    • num不是格式良好的BCMath数值字符串。
    • scale超出有效范围。

    示例

    示例 #1 bcround() 示例

    <?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));
    ?>

    以上示例将输出

    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"

    示例 #2 使用bcround() 和不同precision值的示例

    <?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));
    ?>

    以上示例将输出

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

    示例 #3 使用bcround() 和不同mode值的示例

    <?php
    echo '舍入模式与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     '舍入模式与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));
    ?>

    以上示例将输出

    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"

    示例 #4 使用 bcround() 函数及不同 mode 值指定 precision 精度的示例

    <?php
    echo '使用 RoundingMode::HalfAwayFromZero 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::HalfAwayFromZero));
    var_dump(bcround(-1.55, 1, RoundingMode::HalfAwayFromZero));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::HalfTowardsZero 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::HalfTowardsZero));
    var_dump(bcround(-1.55, 1, RoundingMode::HalfTowardsZero));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::HalfEven 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::HalfEven));
    var_dump(bcround(-1.55, 1, RoundingMode::HalfEven));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::HalfOdd 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::HalfOdd));
    var_dump(bcround(-1.55, 1, RoundingMode::HalfOdd));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::TowardsZero 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::TowardsZero));
    var_dump(bcround(-1.55, 1, RoundingMode::TowardsZero));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::AwayFromZero 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::AwayFromZero));
    var_dump(bcround(-1.55, 1, RoundingMode::AwayFromZero));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::NegativeInfinity 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::NegativeInfinity));
    var_dump(bcround(-1.55, 1, RoundingMode::NegativeInfinity));

    echo     PHP_EOL;
    echo     '使用 RoundingMode::PositiveInfinity 进行小数点后一位精度舍入' . PHP_EOL;
    var_dump(bcround( 1.55, 1, RoundingMode::PositiveInfinity));
    var_dump(bcround(-1.55, 1, RoundingMode::PositiveInfinity));
    ?>

    以上示例将输出

    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"

    参见

    • bcceil() - 向上舍入任意精度数字
    • bcfloor() - 向下舍入任意精度数字

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