Validate an integer in PHP

Question

In the following code, what can we replace `condition` with so as to output `"Integer is valid"` ?
```php 
$int = 100;
if (condition) {
	echo("Integer is valid");
} else {
	echo("Integer is not valid");
}
```

Accepted Answer

`!filter_var($int, FILTER_VALIDATE_INT) === false`

Accepted Answer

`!filter_var($int, FILTER_VALIDATE_INT) == 0`

Answer

`filter_var($int, FILTER_VALIDATE_INT) === true`

Answer

None of these answers

Question from the PHP - Fundamentals test

Validate an integer in PHP