Custom Laravel Blade Directive Always Interprets Bool as True

I'm working on a Laravel 9 project and wanted to create a custom Blade directive that takes in a bool and if it's "true" adds style="display: none;" (so I don't need to use @if... @endif)

In my App\Providers\AppServiceProvider.php I added the following in the boot() method:

Blade::directive('fadeIn', function (bool $fade_in) {
    if ($fade_in) {
        return 'style="display: none;"';
    }
});

And using it like so in my Blade template:

<div @fadeIn(false)></div>

And even though I pass "false" it still returns/adds style="display: none;" as if I passed "true" to it.

I've ran php artisan view:clear (as the directive's function is cached and won't update on any changes) and that doesn't seem to fix things. Removing the parameter type doesn't work either.

Blade directives receive the expression inside the parenthesis, (...).

Directives do not run at the time the template is executed. They are ran as the Blade template is being compiled to PHP. Directives replace things, they don't run at run time. So you need to return what you want the directive to be replaced with at the time it runs.

function ($expression) {
    return "<?php echo ({$expression}) ? 'style=\"display: none;\"' : ''; ?>";
}

This would replace that Blade directive with what is returned, which is just text, that just happens to be valid PHP. So, when the compiled template is actually executed (since it is just a PHP file) it will run that PHP that we have now compiled into it. This means it will actually be dynamic since we now have PHP code that we have in the template that will run at run time and can make use of the expression.

Resulting text in compiled PHP file; based on your example usage:

<?php echo (false) ? 'style="display: none;"' : ''; ?>

To explain why you are seeing what you are seeing in your version:

The directive's function receives the expression not the value; it receives the text, it is not code in the context of executing code, it is just arbitrary text. You are forcing that string to be a boolean with the type-hint: true === (bool) 'false'.

Even if you removed the type-hint and received the string properly your conditional would cause type-juggling and it would be converted to a boolean; which again: true === (bool) 'false'.

On a side note, all strings are true except the "falsey" strings: '0', ''.