Probably a wrong logical operator

[zeleznypa]

Presumably what is meant here is a situation where the input value is validated to boolean and if it is not a boolean, it should return null instead of false.

Except that in this case, the behavior is that the text string 'NULL_ON_FAILURE' only works for 'FILTER_VALIDATE_BOOLEAN' and otherwise ends up with an error Undefined constant "FILTER_FLAG_NULL_ON_FAILURE".

https://github.com/picocms/Pico/blob/09aa82578710d82dd7dc482febe32991be0ea307/lib/Pico.php#L2572C51-L2572C53

However, when reversing the logic, 'NULL_ON_FAILURE' to 'FILTER_VALIDATE_BOOLEAN' is not always applied because $flags can be an empty array.

So personally, I find the && ($filters === FILTER_VALIDATE_BOOLEAN) part to be unnecessary

[PhrozenByte]

That was introduced to better distinguish the behaviour of validate and sanitize filters. Pico::filterVariable() aims to be used in Twig, thus it's a little stricter (nowadays we call that "opinionated" 😆) on how it's supposed to be used. Validate filters are supposed to return the original value if it's valid, or false otherwise. Sanitize filters are supposed to always return a sanitized value, or the default value.

However, for FILTER_VALIDATE_BOOLEAN the idea of a validate filter to return the original value is ambiguous in case of false, since false is a valid boolean, yet it's also used to yield an invalid value. Throwing an exception for an invalid value would have been better, but as I said, Pico::filterVariable() aims to be used in Twig, and Twig doesn't really support exception handling.

So, generally we don't want NULL_ON_FAILURE because it breaks the idea about validate and sanitize filters outlined earlier, yet we need it for a single use case:

if ($this->getPico()->filterVariable($someInput, 'boolean', false, [ 'null_on_failure' ]) !== null) {
    /* valid input */
}

If you want to use NULL_ON_FAILURE in your Pico plugin, you could always use PHP's filter_var() directly. For Pico themes I'd like to ask what you want to achieve first.

[github-actions]

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