SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.
Hi, this is very odd. I guess you are trying to install the latest piwik version.
The last time someone had this error is three years ago: General error: 2014
What version of PHP and MySQL are you using?
You can try commenting out the line including $this->_connection->setAttribute in core/Db/Adapter/Pdo/Mysql.php and check if you are able to setup piwik this way.
parent::_connect();
// MYSQL_ATTR_USE_BUFFERED_QUERY will use more memory when enabled
// $this->_connection->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
$this->_connection->exec('SET sql_mode = "' . Db::SQL_MODE . '"');