Source

File: wp-includes/rest-api.php

function rest_is_object( $maybe_object ) {
	if ( '' === $maybe_object ) {
		return true;
	}

	if ( $maybe_object instanceof stdClass ) {
		return true;
	}

	if ( $maybe_object instanceof JsonSerializable ) {
		$maybe_object = $maybe_object->jsonSerialize();
	}

	return is_array( $maybe_object );
}