Fatal error: Uncaught TypeError: myFunction()

[bertrc]

function myFunction(bool $value = null) : bool {

}
$value = myFunction();
$value = myFunction(true);
echo $value;

Fatal error: Uncaught TypeError: myFunction(): Return value must be of type bool, none returned in /var/www/html/php8/ch5/myValue.php:42 Stack trace: #0 /var/www/html/php8/ch5/myValue.php(43): myFunction() #1 {main} thrown in /var/www/html/php8/ch5/myValue.php on line 42

[sneakyimp]

The error tells you the problem:

Return value must be of type bool, none returned

As I said in your other post, perhaps you should do some remedial reading about functions in php?

[bertrc]

sneakyimp

function myFunction(bool $value = null) : bool {
    return $value;
}
$value = myFunction(false);
echo $value;

$value = myFunction(true);
echo $value;
?>

false do not return 0, only true return 1

[NogDog]

bertrc false do not return 0, only true return 1

Instead of just echo-ing the result, use var_dump($value), instead. (echo will type-cast the Boolean value to a string value, which in this case casts true to "1" and false to "".)

$ php -a
Interactive shell

php > $foo = true;
php > $bar = false;
php > echo $foo;
1
php > var_dump($foo);
bool(true)
php > echo $bar;
php > var_dump($bar);
bool(false))