Fixed parameters

abstract-fixed-parameters.php

<?php
/**
* Controlled way of handling parameter names.
* The script cannot add or read new parameters dynamically.
*/
abstract class FixedParameters
{
	/**
	* Does not allow the script to modify set of parameters later on.
	*/
	public function __set($key='', $value='')
	{
		if(property_exists($this, $key))
		{
			$this->$key = $value;
		}
		else
		{
			throw new Exception('Cannot set value of an undefined key ({$key}).');
		}
	}

	/**
	* Does not allow to read the undefined parameters
	*/
	public function __get($key='')
	{
		if(!property_exists($this, $key))
		{
			throw new Exception("Cannot read undefined key ({$key}).");
		}
		return $this->$key;
	}
}
?>