trait PropertyBag
{
	private function _init()
	{
		$args = func_get_args();
		foreach ($args as $arg)
		{
			$this->local[$arg] = null;
		}
	}
	private function _flag()
	{
		$args = func_get_args();
		if (!empty($args))
		{
			$flag = array_shift($args);
			foreach ($args as $arg)
			{
				$this->flags[$arg] = $flag;
			}
		}
	}
	private function _fail($name)
	{
		$bt = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 2)[1];
		if (!array_key_exists($name, $this->local))
		{
			trigger_error("Invalid property '{$name}' in {$bt['file']}:{$bt['line']}", E_USER_NOTICE);
			return true;
		}
		if (!array_key_exists($name, $this->flags)) return;
		if ($this->flags[$name] == 'ro')
		{
			$fail = 'Read-only';
			if (in_array($bt['function'], ['__get', '__isset'])) return;
		}
		trigger_error("{$fail} property '{$name}' in {$bt['file']}:{$bt['line']}", E_USER_NOTICE);
		return true;
	}
	function __isset($name)
	{
		if ($this->_fail($name)) return;
		return isset($this->local[$name]);
	}
	function __get($name)
	{
		if ($this->_fail($name)) return;
		return $this->local[$name];
	}
	function __set($name, $value)
	{
		if ($this->_fail($name)) return;
		$this->local[$name] = $value;
	}
	function __unset ($name)
	{
		if ($this->_fail($name)) return;
		$this->local[$name] = null;
	}
	function __call($name, $arguments)
	{
		if ($this->_fail($name)) return;
		if (isset($arguments)) $this->local[$name] = $arguments[0];
		return $this->local[$name];
	}
	function set()
	{
		$args = func_get_args();
		if (count($args) > 0) $name = array_shift($args);
		if (count($args))
		{
			$this->local[$name] = $args[0];
		}
		else
		{
			unset($this->local[$name]);
		}
	}
	function getIterator()
	{
		return new ArrayIterator($this->local);
	}
}

class SubAppField implements IteratorAggregate
{
	use PropertyBag;
	private $local = [];
	private $flags = [];
	function __construct()
	{
		$this->_init('id', 'name', 'value');
		$this->_flag('ro', 'value');
	}
}

$fld = new SubAppField();
$fld->id = 'id1';
$fld->name = 'name1';
print_r($fld);
foreach($fld as $key=>&$val) { echo "field {$key} = *{$val}* \n"; $val = 123; }
print_r($fld);

function _assoc($arr)
{
	if (!isset($arr)) return false;
	if (!is_array($arr)) return false;
	if (empty($arr)) return false;
	return array_keys($arr) !== range(0, count($arr) - 1);
}

// Модуль для работы с коллекциями
class Collection implements IteratorAggregate
{

	private $store;

	// new Collection(<field>, [<field>=><value>, ...], ...)
	function __construct()
	{
		$this->store = [];
		$args = func_get_args();
		foreach ($args as $arg)
		{
			if (!isset($arg)) continue;
			if (is_array($arg)) {
				$assoc = _assoc($arg);
				foreach ($arg as $k=>$v)
				{
					if ($assoc) {
						$this->store[$k] = $v;
					} else {
						$this->store[$v] = null;
					}
				}
				unset($assoc, $k, $v);
			} else {
				$this->store[$arg] = null;
			}
		}
	}

	private function _fail($name)
	{
		$bt = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 2)[1];
		if (!array_key_exists($name, $this->store))
		{
			trigger_error("Invalid field '{$name}' in {$bt['file']}:{$bt['line']}", E_USER_NOTICE);
			return true;
		}
	}
	function __isset($field)
	{
		if ($this->_fail($field)) return;
		return isset($this->store[$field]);
	}
	function __get($field)
	{
		if ($this->_fail($field)) return;
		return $this->store[$field];
	}
	function __set($field, $data)
	{
		if ($this->_fail($field)) return;
		$this->store[$field] = $data;
	}
	function __unset ($field)
	{
		if ($this->_fail($field)) return;
		$this->store[$field] = null;
	}
	function __call($field, $arguments)
	{
		if ($this->_fail($field)) return;
		if (isset($arguments)) $this->store[$field] = $arguments[0];
		return $this->store[$field];
	}

	// IteratorAggregate interface
	function getIterator()
	{
		return new ArrayIterator($this->store);
	}

	function _has($field)
	{
		if (isset($field))
		{
			if (array_key_exists($field, $this->store))
			{
				return true;
			}
		}
		return false;
	}

	function _get($field)
	{
		if (isset($field))
		{
			if (array_key_exists($field, $this->store))
			{
				return $this->store[$field];
			}
		}
	}

	function _set($field, $data)
	{
		$this->store[$field] = $data;
		return $this->store[$field];
	}

	function _del($field)
	{
		$item = $this->_get($field);
		if (isset($item)) unset($this->store[$field]);
		return $item;
	}

	function _cnt()
	{
		return count($this->store);
	}

	function _rst()
	{
		$this->store = [];
	}

}

$tmp = new Collection('int', 'str', 'arr', 'ref');
$tmp->int = 123;
$tmp->str('abc');
$tmp->_set('arr', [1,2,3]);
$tmp->ref = new Collection('test');
$tmp->ref->test = 'test1';
print_r($tmp);