Since this extension uses MySQL protocol to access Sphinx, it shares base approach and much code from the regular "yii\db" package. Running SphinxQL queries a very similar to regular SQL ones:
$sql = 'SELECT * FROM idx_item WHERE group_id = :group_id';
$params = [
'group_id' => 17
];
$rows = Yii::$app->sphinx->createCommand($sql, $params)->queryAll();
You can also use a Query Builder:
use yii\sphinx\Query;
$query = new Query();
$rows = $query->select('id, price')
->from('idx_item')
->andWhere(['group_id' => 1])
->all();
Note: Sphinx limits the number of records returned by any query to 10 records by default. If you need to get more records you should specify limit explicitly.