Issue: https://github.com/php/php-src/issues/10326
Author: othercorey
### Description
The following code:
```php
<?php
$r = new ReflectionMethod('XSLTProcessor::transformToXml');
var_dump((string)$r->getReturnType());
```
Resulted in this output:
```
string|null|false
```
But I expected this output instead:
```
string|false
```
Looks like the only null return path was changed in https://github.com/php/php-src/commit/345703724c633fb8c1b34e1299bf3375f000c398
and now only returns false on error.
### PHP Version
8.1
### Operating System
_No response_