src/ActiveQuery.php
public function column($column, $db = null)
    {
        if ($this->emulateExecution) {
            return [];
        }

        // TODO add support for orderBy
        return $this->executeScript($db, 'Column', $column);
    }
public function column($column, $db = null)
    {
        if ($this->emulateExecution) {
            return [];
        }

        // TODO add support for orderBy
        return $this->executeScript($db, 'Column', $column);
    }
Executes the query and returns the first column of the result.
@param string $column name of the column to select
@param Connection $db the database connection used to execute the query.
If this parameter is not given, the `db` application component will be used.
@return array the first column of the query result. An empty array is returned if the query results in nothing.