[php-src] Issue #12143: Incorrect `round(0.49999999999999994, 0, PHP_ROUND_HALF_UP)` result

Issue: https://github.com/php/php-src/issues/12143 Author: TimWolla ### Description The following code: ```php <?php var_dump(round(0.49999999999999994, 0, PHP_ROUND_HALF_UP), 0.49999999999999994); ``` Resulted in this output: ``` float(1) float(0.49999999999999994) ``` But I expected this output instead: ``` float(0) float(0.49999999999999994) ``` ----------------------- Extracted from https://github.com/php/php-src/pull/12056#discussion_r1316488935 into a dedicated issue. The solution consists of using modf() and then explicitly checking against 0.5, instead of adding or subtracting 0.5, since the result of the addition / subtraction might not be exactly representable. /cc @jorgsowa Are you interested in developing the fix? ### PHP Version 8.2.10 ### Operating System _No response_