intval() with negative base prefixed string does not detect base

[Girgias]

Description

The following code:

<?php
$s = "-0b11111111111111111111111111111111111111111111111111111111111111111111111111111";
$v1 = intval($s, 2);
var_dump($v1);
$v2 = intval($s);
var_dump($v2);
var_dump((int) $s);

Resulted in this output:

int(-9223372036854775808)
int(0)
int(0)

But I expected this output instead:

int(-9223372036854775808)
int(-9223372036854775808)
int(0)

Similarly, if we use $base = 16

Note the 0o prefix is not supported (which is what initially led me down this rabbit hole).

PHP Version

PHP 8.3

Operating System

No response

[Girgias]

What is strange is that this works for positive prefixed integers, even with an (int) cast.

Not totally sure what the behaviour is/was meant to be for overflows of negative numbers.

Edit: it turns out this has never worked for negative integers, which is a behaviour: https://3v4l.org/o8inp

[hormus]

Hi @Girgias.

<?php

$i_max = '115792089237316195423570985008687907853269984665640564039457584007913129639936';
$i_max = (int) $i_max;
$i_min = -$i_max - 1;
$s = decbin($i_max);
$v = intval('0b'.$s);
//$v = intval('0b'.$s, 0); // === $i_max
var_dump($s, $v, $i_min);

?>

Actual result:

string(63) "111111111111111111111111111111111111111111111111111111111111111"
int(0)
int(-9223372036854775808)

Expected result:

string(63) "111111111111111111111111111111111111111111111111111111111111111"
int(0)
int(-9223372036854775808)

intval(mixed $value, int $base = 10): int

If base is 0, the base used is determined by the format of value:
If string binary integer > decbin($i_max) overflow to decbin($i_max), if with - sign and < decbin($i_min) underflow to decbin($i_min)

Example 1 string Integer overflow on a 64-bit system

<?php
$i_max = (int) '9223372036854775808';
var_dump($i_max); // 9223372036854775807
?>

Example 2 binary Integer overflow on a 64-bit system

<?php
$a = 0b1000000000000000000000000000000000000000000000000000000000000000;
ini_set('serialize_precision', 19);
var_dump($a);
?>

Actual result:

float(9223372036854774784)