How to give db connection in db beginTransaction - yii

Question

$transaction = Yii::app()->db->beginTransaction();
try {
$transaction=$connection->beginTransaction();
$model = new UserRole();
$model->role_name="new";
$model->save();
$transaction->commit();
Yii::log('Done', 'trace', 'stripe');
}
catch (Exception $e) {
$transaction->rollback();
}
Why data's are insert in db after that begintransaction in yii,What is $connection?i dont exactly what is meaning of $connection.
In My config.php My Db connection like below.
'db' => require(dirname(__FILE__) . '/database.php'),
$connection = array(
'connectionString' => "mysql:host=localhost;dbname=xxx",
'username' => "root",
'password' => "",
'charset' => 'utf8',
'emulatePrepare' => true,
'tablePrefix' => 'tbl_',
);
My databse connection in another file database.php
I got error like,
Call to a member function beginTransaction() on a non-object.
Why data's are not insert after that beginTransaction?

Answer 1

1. set correct db connection params in your config file:
'db' => array(
'connectionString' => "mysql:host=localhost;dbname=xxx",
'username' => "root",
'password' => "",
'charset' => 'utf8',
'emulatePrepare' => true,
'tablePrefix' => 'tbl_',
)
or write connection data in database.php and include it in main config:
in database.php
return array(
'connectionString' => "mysql:host=localhost;dbname=xxx",
'username' => "root",
'password' => "",
'charset' => 'utf8',
'emulatePrepare' => true,
'tablePrefix' => 'tbl_',
);
in main.php (or other config file)
'db' => require(dirname(__FILE__) . '/database.php'),
2. define $connection varaible before using:
$connection = Yii::app()->db;
try {
$transaction = $connection->beginTransaction();
$model = new UserRole();
$model->role_name = "new";
$model->save();
$transaction->commit();
Yii::log('Done', 'trace', 'stripe');
} catch (Exception $e) {
if (isset($transaction)) {
$transaction->rollback();
}
Yii::log('Error', 'trace', 'stripe');
}