Collection::has

public function has(EntityObject $object)
{
	// check object class
	if (!($object instanceof $this->_objectClass))
	{
		throw new ArgumentException(sprintf(
			'Invalid object class %s for %s collection, expected "%s".',
			get_class($object), get_class($this), $this->_objectClass
		));
	}

	return array_key_exists($this->sysGetPrimaryKey($object), $this->_objects);
}