<?php
function someFunction(int|float $number) {}
$reflectionFunc = new ReflectionFunction('someFunction');
$reflectionParam = $reflectionFunc->getParameters()[0];
var_dump($reflectionParam->getType()->getTypes());
The above example will output
something similar to:
array(2) {
[0] =>
class ReflectionNamedType#4(0) {
}
[1] =>
class ReflectionNamedType#5(0) {
}
}