class Date_Calculate
{
    private $m_iFromTimestamp;
    
    public function __call($szCall, $aArgs)
    {
        if (preg_match('~^to(Minus|Plus)(\d+)(.+)$~i', $szCall, $aMatches))
        {
            $szOperator = $aMatches[1] == 'Minus' ? '-' : '+';
            $iTimestamp = !empty($this->m_iFromTimestamp) ? $this->m_iFromTimestamp : time();
            return date($aArgs[0], strtotime($szOperator . $aMatches[2] . ' ' . $aMatches[3], $iTimestamp));
        }
        
        throw new Exception('Invalid date to syntax specified');
    }
    
    public function from($iTimestamp)
    {
        if (!is_integer($iTimestamp))
        {
            $iTimestamp = strtotime($iTimestamp);
        }
        
        $this->m_iFromTimestamp = $iTimestamp;
        return $this;
    }
}

$pDate = new Date_Calculate();

echo $pDate->from(time())->toMinus4Days('jS M Y');
echo $pDate->toPlus5Years('jS M Y');