max/min return wrong value if signed (negative) zero

[kkmuffme]

Description

The following code:

https://3v4l.org/JXU4T#v8.4.13

<?php
var_dump( min( round( -0.01 / 2, 0 ), 0 ) );
var_dump( max( round( -0.01 / 2, 0 ), 0 ) );

Resulted in this output:

int(0)
float(-0)

But I expected this output instead:

float(-0)
int(0)

For 99.9% of applications, this output is actually what people would expect however: (instead of -0)

float(0)
int(0)

so I guess it would make sense to also change that.

This does not have any impact on calculations or comparisons, this is purely visual but can lead to unexpected behavior if the returned number is used as a string (e.g. substr, strtok,...) since there suddenly is an additional character in front of the numbers.
This is especially unexpected, when the float is the result of float arithmetics, which can minimally negative numbers in some cases

PHP Version

8.4

Operating System

No response

[nielsdos]

Versions prior to 8.4 output:

float(-0)
float(-0)

[TimWolla]

Changing the order of the parameters

<?php
var_dump( min( 0, round( -0.01 / 2, 0 ) ) );
var_dump( max( 0, round( -0.01 / 2, 0 ) ) );

returns:

float(-0)
int(0)

So this seems to be related to how 0.0 and -0.0 compare equal and thus the behavior is returning either the first or the last of all equal values.

[TimWolla]

Simpler reproducer:

<?php
var_dump(min(0.0, -0.0));
var_dump(min(-0.0, 0.0));
var_dump(max(0.0, -0.0));
var_dump(max(-0.0, 0.0));

[TimWolla]

JavaScript:

> Math.min(0.0, -0.0);
-0
> Math.min(-0.0, 0.0);
-0
> Math.max(-0.0, 0.0);
0
> Math.max(0.0, -0.0);
0

[TimWolla]

Full test case:

<?php
foreach ([-0.0, 0.0] as $a) {
	foreach ([-0.0, 0.0] as $b) {
		if ("$a $b" === "0 0" || "$a $b" === "-0 -0") {
			continue;
		}

		printf("min(%.17g, %.17g)   = %.17g\n", $a, $b, min($a, $b));
		printf("min([%.17g, %.17g]) = %.17g\n", $a, $b, min([$a, $b]));
		printf("max(%.17g, %.17g)   = %.17g\n", $a, $b, max($a, $b));
		printf("max([%.17g, %.17g]) = %.17g\n", $a, $b, max([$a, $b]));
		echo "\n";
	}
}

echo "======\n\n";

foreach ([-0.0, 0.0] as $a) {
	foreach ([-0.0, 0.0] as $b) {
		foreach ([-0.0, 0.0] as $c) {
			if ("$a $b $c" === "0 0 0" || "$a $b $c" === "-0 -0 -0") {
				continue;
			}

			printf("min(%.17g, %.17g, %.17g)   = %.17g\n", $a, $b, $c, min($a, $b, $c));
			printf("min([%.17g, %.17g, %.17g]) = %.17g\n", $a, $b, $c, min([$a, $b, $c]));
			printf("max(%.17g, %.17g, %.17g)   = %.17g\n", $a, $b, $c, max($a, $b, $c));
			printf("max([%.17g, %.17g, %.17g]) = %.17g\n", $a, $b, $c, max([$a, $b, $c]));
			echo "\n";
		}
	}
}