PHP Conference Nagoya 2025

    bcround

    (PHP 8 >= 8.4.0)

    bcround — Round arbitrary precision number

    说明

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

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

    参数

    num

    要处理的值。

    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 a numeric string representing num rounded to the given precision.

    错误／异常

    This function throws a ValueError in the following cases:

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

    示例

    示例 #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));
    ?>

    以上示例会输出：

    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 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));
    ?>

    以上示例会输出：

    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 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));
    ?>

    以上示例会输出：

    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 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));
    ?>

    以上示例会输出：

    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() - Round up arbitrary precision number
    • bcfloor() - Round down arbitrary precision number

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