I'm not sure if this really fixes the problem.

Example:

public function doBar()
{
    $isAbc = MyClass::class === ABC;
}

I'll find "ABC" as a class name.

It seems that the problm is on line 114/116, i.e. the condition:

if (T_CLASS === $token[0]) {

because having T_CLASS token doesn't really mean that we've found a class definition.
Until PHP token_get_all() function can differentiate between class MyClass { ... (which is really a class definition), and MyClass::class (which isn't), I think this condition needs to be extended, e.g.:

$previousTokenIsPaamayimNekudotayim = isset($tokens[$i - 1]) && T_PAAMAYIM_NEKUDOTAYIM === $tokens[$i - 1][0];
if (T_CLASS === $token[0] && !$previousTokenIsPaamayimNekudotayim) {
    $class = true;
}

As I said this is not ready yet. Thanks for feedback so far!