Question resolved.

Not a kata suggestion. Resolved.

The error you see happens before the check. The error is raised in line 2, and your check is too late, in line 3.

It's a bug in your solution, not a kata issue.

That's a problem with your code, not with the kata.

I don't get it ? ...isn't supposed to be simple fundamentals ?
I write in JS so typeof is default XD

Can someone with edit abilities please add the following 3 tests to the Error Test Cases section. Currently this specific test is only being done for +, not the other operators, and it's allowed some solutions to get through (and be highly upvoted) that don't actually meet all the requirments in the description.

test.assert_equals(calculator(":", ",", '-'),"unknown value")
test.assert_equals(calculator(":", ",", '*'),"unknown value")
test.assert_equals(calculator(":", ",", '/'),"unknown value")

BRO you are my savior xd, thanks

what's wrong?
error of all tests:
Failed asserting that null matches expected 3.
Expected: 3
Actual : null
in sandbox all works
function calculator($a, $b, $sign) {
if ( is_int($a) & is_int($b) ) {
switch ($sign) {
case "+":
$c = $a+$b;
break;
case "-":
$c = $a-$b;
break;
case "":
$c = $a$b;
break;
case "/":
if ($b == 0) {
$c = "unknown value";
} else {
$c = $a/$b;
}
break;
default:
$c = "unknown value";
}
} else {
$c = "unknown value";
}
echo $c;
}

I think it is not a spoiler and it must be reported. I've lost 2 hours to find this information! "type(x) == int" checks that x is a number! It will be very important for many people!

For some reason I cannot resolve this issue, can someone else please do it?