Type hinting generic objects

Since PHP objects don’t inherit from any base class (including stdClass), there is no support for type hinting a generic object type.

For example, the below will not work.

<?php

function doSomething(object $obj) {
    return $obj;
}

class ClassOne {}
class ClassTwo {}

$classOne= new ClassOne();
$classTwo= new ClassTwo();

doSomething($classOne);
doSomething($classTwo);

And will throw a fatal error:

Fatal error: Uncaught TypeError: Argument 1 passed to doSomething() must be an instance of object, instance of OperationOne given

A workaround to this is to declare a degenerate interface that defines no methods, and have all of your objects implement this interface.

<?php

interface Object {}

function doSomething(Object $obj) {
    return $obj;
}

class ClassOne implements Object {}
class ClassTwo implements Object {}

$classOne = new ClassOne();
$classTwo = new ClassTwo();

doSomething($classOne);
doSomething($classTwo);