Cdbconnection failed to open the db connection

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CDbException: CDbConnection could not open database connection

I started getting this error while trying to do a yiic migration on my experimental project.

CDbException: CDbConnection could not open database connection

Googling I realized that pdo_mysql.sono was present as a module in my PHP installation. So I had to recompile PHP 5.2.10, with the


configured option.

This fixed the problem!

I also added –with-mysql and –with-mysqlq to the config. With this you can remove the extension in php.ini, as the old MySQL configuration would no longer require a dynamic extension.

To verify that MySql PDO is installed, type php -m and verify that there is an entry for pdo_mysql.

CDbConnection could not open DB Yii connection


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When I try to connect to mysql with plain PHP it works fine. My code

$link = mysql_connect(‘hostname’, ‘username’, ‘password’); if (!$link) { die(‘Failed to connect’); } if(mysql_select_db(‘dbname’)){ echo ‘Connected successfully’; }

But when I try to connect with yii I get the error


‘db’=>array( ‘class’=>’CDbConnection’, ‘connectionString’ => ‘mysql:host=hostname;dbname=dbname’, ’emulatePrepare’ => true, /* I’m also trying false*/ ‘ username ‘ => ‘username’, ‘password’ => ‘password’, ‘charset’ => ‘utf8’, ),

This is the output of the exception I print in the open() function framework/db/CDbConnection.php Exception handle here

protected function open() { if($this->_pdo===null) { if(empty($this->connectionString)) throw new CDbException(‘CDbConnection.connectionString cannot be empty.’); try { Yii::trace(‘Opening database connection’, ‘system.db.CDbConnection’); $this->_pdo=$this->createPdoInstance(); $this->initConnection($this->_pdo); $this->_active=true; } catch(PDOException $e) { echo ‘<pre>’; var_dump($e); die; if(YII_DEBUG) { throw new CDbException(‘CDbConnection failed to open database connection: ‘. $e->getMessage(),(int)$e->getCode(),$e- >errorInfo); } else { Yii::log($e->getMessage(),CLogger::LEVEL_ERROR,’exception.CDbException’); throw new CDbException(‘CDbConnection n’ failed to open database connection.’,(int)$e->getCode(),$e->errorInfo); } } } }

exception text

“SQLSTATE[HY000] [2054] The server requested an authentication method unknown to the client”

I see on the screen

CDbException CDbConnection failed to open the database connection.

My PHP VERSION 5.5.36 Mysql version 5.5.35 My hosting is i-page dot com Yii Version ‘1.1.13’ Thanks for the help.

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requested on April 2, 2014 at 3:00 p.m.

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styopdev styopdev

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    Je vérifie juste, mais le tableau ‘db’ est-il dans le tableau ‘components’ de votre main/config.php? Pouvez-vous également coller comment vous utilisez la fonction d’ouverture de CDbConnection ?

    – ews2001

    2 avril 2014 à 20:56

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    3 avril 2014 à 5:46

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There seems to be a problem with the way passwords are hashed and the version of MySQL and the MYSQL_PDO library.

Yii uses PDO to query the database, that’s why plain PHP works like a charm and Yii doesn’t.

To verify this, try this:

$mysqlConnection = new PDO(“mysql:host=hostname;dbname= dbname”, “username”, “password”);

this line should return the following error:

PDO::__construct(): The server requested authentication method unknown to the client [mysql_old_password].

This error is the equivalent to the MySQL 2045:

“SQLSTATE[HY000] [2054] The server requested authentication method unknown to the client

If you confirm that the problem is related to PDO you have several options but you need to access the hosting system (or ask them to fix the problem):

  • Sign in to MySQL and execute the following command SET PASSWORD FOR ‘username’@’hostname’ = OLD_PASSWORD(‘password’); (this will fix the hashing of the password)
  • Upgrade the MYSQL PDO Library (PDO_MYSQL) to match the version of MYSQL on the server.


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answered Apr 3, 2014 at 3:36 PM

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  • Hi, thanks for the reply. But I don’t have webserver admin permission because I just use web hosting, I think hosting admin need to do it. When I have solved this problem, I will post the solution.

    – styopdev

    April 3, 2014 at 7:02 PM

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I had this problem with the Yii 1.1.x project and almost went crazy:

First make sure you have

sudo apt install php-xml php-mbstring php-pdo php-mysql

installed and restart apache

sudo apachectl restart


sudo apache2 service restart

The detailed error was that the database library could not be found .

My solution was related to caching:

cache’ => array( ‘class’ => ‘system.caching.CDbCache’, //’class’ => ‘system.caching.CFileCache’, ‘connectionID’=>’db’, // <<< C’ IS THE PROBLEM),

si connectionID n’est pas défini, la mise en cache de la base de données utilise par défaut la base de données mysqli dans le répertoire /protected/data qui n’est pas accessible si le pilote mysqli n’est pas installé sur le système (problème courant avec les serveurs dédiés, les gouttelettes DO, xampp/wamp …)

ou, vous pouvez désactiver la mise en cache db et activer fileCache à la place.


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modifié le 3 juin 2018 à 17:22

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