问找不到pdo_mysql驱动程序导致的IIC卡迁移错误

EN

exception 'CDbException' with message 'CDbConnection failed to open the DB connection: could not find driver' in /var/www/yii/framework/db/CDbConnection.php:382

`if($this->_pdo===null)
 {
    if(empty($this->connectionString))
         throw new CDbException('CDbConnection.connectionString cannot be empty.');
    try
    {
         Yii::trace('Opening DB connection','system.db.CDbConnection');
         $this->_pdo=$this->createPdoInstance();
         $this->initConnection($this->_pdo);
         $this->_active=true;
    }
    catch(PDOException $e)
    {
        if(YII_DEBUG)
        {
           throw new CDbException('CDbConnection failed to open the DB connection:'.

                                  $e->getMessage(),(int)$e->getCode(),$e->errorInfo);

        }
        else
        {                                        
           Yii::log($e->getMessage(),CLogger::LEVEL_ERROR,'exception.CDbException');

           throw new CDbException('CDbConnection failed to open the DB connection.' 

                                  ,(int)$e->getCode(),$e->errorInfo);
    }
    }
}

php -i|grep PDO gives 
PDO
PDO support => enabled 
PDO drivers => sqlite
PDO Driver for SQLite 3.x => enabled