Fatal error: Class 'DB_common' not found in mysql.php on line 46

\\\\\\\\\

class DB_mysql extends DB_common
{
    // {{{ properties

    var $connection;
    var $phptype, $dbsyntax;
    var $prepare_tokens = array();
    var $prepare_types = array();
    var $num_rows = array();
    var $transaction_opcount = 0;
    var $autocommit = true;
    var $fetchmode = DB_FETCHMODE_ORDERED; /* Default fetch mode */
    var $_db = false;