Numbers starting with 0 fail validation using FILTER_VALIDATE_INT

[ollieread]

Description

The following code:

<?php

declare(strict_types=1);

var_dump(filter_var('00', FILTER_VALIDATE_INT));
var_dump(filter_var('0', FILTER_VALIDATE_INT));
var_dump(filter_var('01', FILTER_VALIDATE_INT));
var_dump(filter_var('1', FILTER_VALIDATE_INT));

Resulted in this output:

bool(false)
int(0)
bool(false)
int(1)

But I expected this output instead:

int(0)
int(0)
int(1)
int(1)

PHP Version

PHP 8.1.4

Operating System

No response

[KapitanOczywisty]

Seems like this is intentional, since 0 prefix means octal and to parse octal numbers, the FILTER_FLAG_ALLOW_OCTAL flag is required. https://3v4l.org/5oiFQ

[cmb69]

Hmm, I believe this is by design, because the 0 prefix may mark octal numbers (see https://3v4l.org/IKJ93). However, it might not have been the best design.

[ollieread]

@KapitanOczywisty @cmb69 I can see from the code that it allows a starting 0 and then checks for hex or octal, then just stops if there's any more characters.

The problem is, technically, 00 is valid, it's just 0. It's no less valid than 0_0.

https://3v4l.org/n9gAL

[cmb69]

https://3v4l.org/n9gAL

That's comparing apples to oranges (see https://3v4l.org/Lhedi). :)

But yeah, like I said:

However, it might not have been the best design.

[iluuu1994]

As the behavior is expected and there is even an option to change it I'm closing this issue.

[ollieread]

As the behavior is expected and there is even an option to change it I'm closing this issue.

That's a fair point, but is there something to be done in terms of a discussion around this? I appreciate that it was intended, but it doesn't make much sense. PHP itself will accept 00 or 01 being passed to an int parameter with strict types enabled, and is_int(00) will return true (https://3v4l.org/c13Ad).

This seems like another time where we've accidentally introduced an inconsistency.