PHP PDOStatement: fetch a row, as the first column as the key of an array

I am using PDOStatement to query the database. Whenever I get a returned row, I want it to be fetched into an array, with the $row[0] as the key, and the subsequent elements in the row as the values.

I can, of course, write a combination of foreach loops and if conditionals to do the job, such as the below:

private static function GetMySQLResult($dbname, $sqlString) {
    
    $dbh = self::ConstructPDOObject($dbname);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $result=array();
    foreach ($dbh->query($sqlString) as $row) {
        // the simplest case for 2 columns, 
        // should add more to handle more columns
        $result[$row[0]][]=$row[1];
    }
    
    return $result;   
}

but I am looking for an existing method; is there such a method already exist?

Why reopened the question.

What is asked here is clearly the combination of PDO::FETCH_GROUP|PDO::FETCH_ASSOC. PDO::FETCH_KEY_PAIR only works with a 2 column result. But here the example is a 2 column result only to simplify the code in the question, not for all situations.