function broker()

[wangdicnyz]

public function broker($address, $port, $clientid, $cafile = null): void{

}

php 7.0 no working please tell me php number

[anhlephuoc]

php 7.3 or later should be OK.
If you can't upgrade php then just remove the :void, but that would only defer the problem to return and haunt you at a future date.