为什么Laravel调用execute（）会返回重复的结果？

Question

I'm a new, inexperienced Laravel developer and I'm confused by the query results I'm getting. I'm trying to write to results of a query to a CSV file. My code:

$connection = fopen('/BSTablespace/someFile.txt', 'w');

$users = DB::table('users')->select('first_name', 'agent_id_from_website', 'sales_manager_id', 'last_name')->toSql();

$generator = function () use ($users){
        $db = DB::connection()->getPdo();

        $query = $db->prepare($users);
        $query->execute();

        while($user = $query->fetch()){
            yield($user);
        }
    };

foreach ($generator() as $g){
        fputcsv($connection, array_values($g));
    }
fclose($connection);

Instead of getting one result per column, I get 2. One keyed with the column name and one keyed with a numeric index, like so:

'first_name' => 'Jane', 0 => 'Jane', 'agent_id_from_website' => '450', 1 => '450', 'sales_manager_id' => 317, 2 => 317, 'last_name' => 'Doe', 3 => 'Doe'

Why am I getting duplicate results? Obviously I can just ignore the duplicates but I'm very curious as to why PHP, Laravel, or Postgres handles it this way.

Answer 1

Why are you not just doing ->get()? You're getting weird results because that's how the PHP PDO works. These \Illuminate\DB methods you're using are basically touching the PDO directly.

http://php.net/manual/en/pdostatement.fetch.php

It returns both the sequential values and the given name of the statement. This is probably to deal with instances where there are unnamed columns returned.