A class which can stores methods to be executed when certain events happen. It can also be accessed via object notation or arrayaccess. These Meta Methods are fired on events such as attempting to access an unset variable and can be used to return another value such as default value. This is however just the begining.

Meta Tables

<?php
/*   --  Meta Methods  --
NewIndex  - When a new index is added
Modify    - When an element is changed
Isset     - When isset() is ran on a value
Unset     - When unset() is ran
Index     - When an element is requested that does not exist
Count     - When count() is ran. This will exclude MetaMethods when counting elements
*/

class MetaTable implements arrayaccess, Countable, IteratorAggregate {
	public $_data = array();
	private $_Config = array(
		"MetaPrefix" => "__"
	);

	public function __construct(array $Data) {
		$this->_data = $Data;
	}

	public function AddMeta($Offset, $Value){ //Metas should not be able to intervene when dealing with other Metas
		$this->_data[$this->_Config["MetaPrefix"] . $Offset] = $Value;
	}

	public function RemoveMeta($Offset){ //Metas should not be able to intervene when dealing with other Metas
		unset($this->_data[$this->_Config["MetaPrefix"] . $Offset]);
	}

	public function GetMeta($Offset){ //Metas should not be able to intervene when dealing with other Metas
		return $this->_data[$this->_Config["MetaPrefix"] . $Offset];
	}

	/** ------------------- Helpers ------------------- **/

	private function HasMeta($Value){
		return (isset($this->_data[$this->_Config["MetaPrefix"] . $Value])) ? true : false;
	}

	private function CallMeta($Value, $Params = array()){
		if(is_callable($this->_data[$this->_Config["MetaPrefix"] . $Value])){
			return $this->_data[$this->_Config["MetaPrefix"] . $Value]($this, $Params);
		} else {
			return $this->_data[$this->_Config["MetaPrefix"] . $Value];
		}
	}

	private function IsolateElements(){ //Returns an array that excludes all Meta Methods
		$ElementsArray = array();
		foreach ($this->_data as $key => $value) {
			$StringPos = strpos($key, $this->_Config["MetaPrefix"]);
			if ($StringPos === false || $StringPos != 0) {
				$ElementsArray[$key] = $value;
			}
		}
		return $ElementsArray;
	}

	/** ------------------- Array Access ------------------- **/

	public function offsetSet($offset, $value) {
		if (is_null($offset)) {
			if($this->HasMeta("NewIndex") === false){
				$this->_data[] = $value;
			} else {
				$this->_data = $this->CallMeta("NewIndex", array("Value" => $value, "Offset" => $offset));
			}
		} else {
			if($this->offsetExists($offset) == false){
				if($this->HasMeta("NewIndex") === false){
					$this->_data[$offset] = $value;
				} else {
					$this->_data = $this->CallMeta("NewIndex", array("Value" => $value, "Offset" => $offset));
				}
			} else {
				if($this->HasMeta("Modify") === false){
					$this->_data[$offset] = $value;
				} else {
					$this->_data = $this->CallMeta("Modify", array("Value" => $value, "Offset" => $offset));
				}
			}
		}
	}

	public function offsetExists($offset) {
		if($this->HasMeta("Isset") === false){
			return isset($this->_data[$offset]);
		} else {
			return $this->CallMeta("Isset", array("Offset" => $offset));
		}
	}

	public function offsetUnset($offset) {
		if($this->HasMeta("Unset") === false){
			unset($this->_data[$offset]);
			return true;
		} else {
			$this->_data = $this->CallMeta("Unset", array("Offset" => $offset));
		}
	}

	public function offsetGet($offset) {
		if(isset($this->_data[$offset]) === false){
			if($this->HasMeta("Index") === false){
				return null;
			} else {
				return $this->CallMeta("Index", array("Offset" => $offset));
			}
		} else {
			return $this->_data[$offset];
		}
	}

	/** ------------------- Object Notation ------------------- **/

	public function __set($offset, $value){
		$this->offsetSet($offset, $value);
	}

	public function __get($offset){
		return $this->offsetGet($offset);
	}

	public function __isset($offset){
		return $this->offsetExists($offset);
	}

	public function __unset($offset){
		return $this->offsetUnset($offset);
	}

	/** ------------------- Iterator ------------------- **/

	public function getIterator() {
        return new ArrayIterator($this->IsolateElements());
    }

	/** ------------------- Count ------------------- **/

	public function count(){ //Does not count MetaMethods
		if($this->HasMeta("Count") === false){
			return count($this->IsolateElements());
		} else {
			return $this->CallMeta("Count");
		}
	}
}