Date Wrapper

dateWrapper.php

class Date{
	public $date;
	public $timestamp;
	private $format = "Y-m-d";

	public function __construct($dateString)
	{
		$this->_setAttrForTimestamp( strtotime($dateString) );
	}

	public function add($amount, $increment)
	{
		$timestamp = strtotime("+$amount $increment", $this->timestamp);
		$this->_setAttrForTimestamp( $timestamp );
	}

	public function subtract($amount, $increment)
	{
		$timestamp = strtotime("-$amount $increment", $this->timestamp);
		$this->_setAttrForTimestamp( $timestamp );
	}

	//  PRIVATE FUNCTIONS
	private function _setAttrForTimestamp($timestamp)
	{
		$this->timestamp = $timestamp;
		$this->date = date( $this->format , $timestamp);
	}

}