private function _generateKey()
    {
        if ($this->_key == '') {
            $this->_key = pack(
                'H*',
                hash('SHA256', md5(uniqid()))
            );
        }

        return $this->_key;
    }
private function _generateKey()
    {
        if ($this->_key == '') {
            $this->_key = pack(
                'H*',
                hash('SHA256', md5(uniqid()))
            );
        }

        return $this->_key;
    }
private function _generateKey ( ) { if ( $ this -> _key == '' ) { $ this -> _key = pack ( 'H*' , hash ( 'SHA256' , md5 ( uniqid ( ) ) ) ) ; } return $ this -> _key ; }
Generates crypt key
@return string
Generates crypt key