if(phpversion() < 5.3){
    class baseException extends Exception{

        /**
         * @var Exception
         */
        protected $previousException;

        /**
         * @param string $message
         * @param int $code
         * @param Exception $previous
         */
        function __construct($message = '', $code = 0, $previous = null) {
            parent::__construct($message, 0);
            $this->previousException = $previous;
        }

        /**
         * @return Exception
         */
        public function getPrevious() {
            return $this->previousException;
        }

        /**
         * @return string
         */
        public function _getTraceAsString() {
            if($this->previousException === null){
                return parent::getTraceAsString();
            }
            if($this->previousException instanceof BaseException){
                return $this->previousException->_getTraceAsString();
            }
            return $this->previousException->getTraceAsString();
        }

        /**
         * @return array
         */
        public function _getTrace() {
            if($this->previousException === null){
                return parent::getTrace();
            }
            if($this->previousException instanceof BaseException){
                return $this->previousException->_getTrace();
            }
            return $this->previousException->getTrace();
        }

        /**
         * @return string
         */
        public function __toString() {
            return "exception '".__CLASS__ ."' with message '".$this->getMessage()
                ."' in ".$this->getFile().":".$this->getLine()
                ."\nStack trace:\n".$this->_getTraceAsString();
        }
    }
} else {
    class baseException extends Exception{
        public function __construct($message, $code = 0, $previous = null) {
            parent::__construct($message, 0, $previous);
        }

        /**
         * @return string
         */
        public function _getTraceAsString() {
            return $this->getTraceAsString();
        }

        /**
         * @return array
         */
        public function _getTrace() {
            return $this->getTrace();
        }
    }
}