PHP 7 and strict "resource" types

Does PHP 7 support strict typing for resources? If so, how?

For example:

	declare (strict_types=1);

	$ch = curl_init ();
	test ($ch);

	function test (resource $ch)
	{

	}

The above will give the error:

> Fatal error: Uncaught TypeError: Argument 1 passed to test() must be an instance of resource, resource given

A var_dump on $ch reveals it to be resource(4, curl), and the manual says curl_init () returns a resource.

Is it at all possible to strictly type the test() function to support the $ch variable?

PHP does not have a type hint for resources because

> No type hint for resources is added, as this would prevent moving from resources to objects for existing extensions, which some have already done (e.g. GMP).

However, you can use is_resource() within the function/method body to verify the passed argument and handle it as needed. A reusable version would be an assertion like this:

function assert_resource($resource)
{
    if (false === is_resource($resource)) {
        throw new InvalidArgumentException(
            sprintf(
                'Argument must be a valid resource type. %s given.',
                gettype($resource)
            )
        );
    }
}

which you could then use within your code like that:

function test($ch)
{
    assert_resource($ch);
    // do something with resource
}

resource is not a valid type so it's assumed to be a class name as per good old PHP/5 type hints. But curl_init() does not return an object instance.

As far as I know there's not way to specify a resource. It probably wouldn't be so useful since not all resources are identical: a resource generated by fopen() would be useless for oci_parse().

If you want to check the resource in the function body, you can use get_resource_type() (with is_resource() to prevent errors), as in:

is_resource($ch) && get_resource_type($ch) === 'curl'

---

Starting on PHP/8.0, curl_init() returns an object so you can now use CurlHandle as type hint,