You can get function reflection by using getFunction from $reflector:
$reflector = new Reflector(Reflector::manuallyFactory());
$reflection = $reflector->getFunction('gettype');Next you can use methods from FunctionReflection, for example:
var_dump($reflection->getNumberOfParameters());
var_dump($reflection->getNumberOfRequiredParameters());At all, you can run function from $reflection
var_dump($reflection->run(array(1))); //float