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PHP0423 seems to be an issue in PHP Tools, where the vararg (...) signature is incorrectly processed:

Will be fixed within the next update.
PHP0406 is caused because of the namespace was not specified, PHPDoc should be:
* @method static Validator optional(\Respect\Validation\Validatable $rule)
or use statement at the top of the script:
use Respect\Validation\Validatable;