CODEWITHSUNDEEP
phpvalidationbooleanfilter-var
RS7
RS7

Reputation: 2361

PHP validation booleans using filter_var

I'm using filter_var to validate boolean values but I did not expect it to not recognize FALSE. Why does this happen?

filter_var(FALSE, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)

returns

null

Upvotes: 10

Views: 12043

Answers (4)

Thanh Trung
Thanh Trung

Reputation: 3804

According to the documentation

Returns true for "1", "true", "on" and "yes". Returns false otherwise.

Anything different than the values mentioned above is considered falsy. This is not to test if a variable is actually a boolean like with typeof or is_bool(), but more like a mean to test if the input comming from the user (usually an <input type="checkbox"> form) is truthy/falsy.

The behavior of this function could be understand as let it go through if it's correct rather than a mean to test the type of a variable (we have lots of other functions for this). Exemple :

filter_var('435345', FILTER_VALIDATE_INT)

The type is a string, but the result is not true/false as the intention is not to validate the type. So an int would be returned (let go through).

Upvotes: 0

apokryfos
apokryfos

Reputation: 40680

This was the behaviour when filter_var was first introduced with version 5.2 and resolved at some point after 5.4 as is seen by this https://3v4l.org/Cv1MZ

Starting from version 5.4 this is what happens:

var_dump(filter_var(FALSE, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE));

bool(false)

which makes much more sense.

Upvotes: 1

Machavity
Machavity

Reputation: 31654

It sounds like this is actually how it's supposed to work, strangely enough (yes, my mind was blown by that). From https://bugs.php.net/bug.php?id=51344

This is going to sound insane when you've looked at the underlying filter code, but this is actually correct according to the documentation: the default behaviour of filter_input() is to return NULL for non-existent inputs and false when validation fails, and FILTER_NULL_ON_FAILURE simply flips that behaviour to false for non-existent inputs and NULL on validation failure. (No, I don't have a clue where that would be useful either, and the name of the flag is unfortunate in the filter_input() context, since it implies that NULL wouldn't normally be returned. It makes more sense when used with filter_var(), which doesn't have the non-existent input case.)

[table omitted due to SO formatting]

I'll pop a comment into the filter_input() and filter_input_array() implementations to note that this is by design, even though the code does kind of look wrong.

Closing Won't Fix.

Upvotes: 3

dkamins
dkamins

Reputation: 21918

filter_var is new as of PHP 5.2. You've run into a known bug: https://bugs.php.net/bug.php?id=49510 Feel free to vote on or comment on that bug.

You're trying to do something like this:

$v = filter_var($v, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)

There are a number of cheap workarounds like this:

$v = $v===FALSE ? FALSE : filter_var($v, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)

Upvotes: 7

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