round 123456789012.1245 failed with precision 2

[AnatoliyDanchuk]

Description

The following code:

<?php
echo round(123456789012.1245, 2);

Resulted in this output:

123456789012.13

But I expected this output instead:

123456789012.12

It reproduced on different OS, different php versions after 5.3.0 (included).
Example in online sandbox:
https://onlinephp.io?s=s7EvyCjg5eLlSk3OyFcoyi_NS9EwNDI2MTUzt7A0MDTSMzQyMdVRMNK0BgA%2C&v=8.3.7

PHP Version

8.3.7

Operating System

No response

[AnatoliyDanchuk]

I see math.h included.
math.h has already round function, and it works fine.

#include <stdio.h>
#include <math.h>

int main() {
double a = round(12345678901212.45);
printf("%f", a);
return 0;
}

so maybe to use something like round(X * pow(10, $precision)) / pow(10, $precision) for round up ...

My workaround in real project:

/**
 * @reason: round(123456789012.1245, 2) return 123456789012.13 instead of 123456789012.12
 *          on 64bit php >= 5.3.0 on dev, on local docker. On last version 8.3.7 the issue is actual.
 * @info: Support qty max 12 + 4, 8 + 8
 * @info: Price expected till 14 + 2.
 * @warning: Supporting of bigger numbers are required string or bigger number type than double
 *           in php, mysql, mongodb, solr.
 *
 * @param string|float|int $number
 * @param string|int $precision
 * @return float|int
 */
public function correctRound($number, $precision)
{
    if (!strpos((string)$number, '.')) {
        return (float)$number;
    }

    $absNumber = abs($number);

    [$int, $decimals] = explode('.', (string)$absNumber);
    $interestedDecimals = substr($decimals, 0, $precision + 1);
    $floatToRound = (float)"0.$interestedDecimals";
    $roundedAbsNumber = $int + round($floatToRound, $precision);

    $roundedNumber = $number > 0 ? $roundedAbsNumber : -$roundedAbsNumber;

    if ($roundedNumber == -0) {
        $roundedNumber = 0;
    }
    return $roundedNumber;
}

[SakiTakamachi]

This is a known issue.

This has already been fixed in master. However, since this change affected all aspects of round(), we were concerned about disrupting existing user environments, so only fixed it in master.

#12268

[SakiTakamachi]

@bukka
Do you think this should be backported?
Fixing this would require major changes to the logic as same as master, so I'm concerned about breaking changes.

[bukka]

yeah I wouldn't back port it. It might do more harm than good.

[SakiTakamachi]

Thanks. This should be fixed in 8.4 and later, so for 8.2 and 8.3 we won't be fixing this.