Converting an Eloquent collection to CSV

collection_to_csv.php

<?php

use \League\Csv\Writer;

$transform = function($collection) {
    $collection->transform(function ($item) {
        $item['institution'] = $item['institution']['name'];
        $item['status'] = $item['status']['status'];
        if ($item['latest_note']){
            $item['latest_note_user'] = $item['latest_note']['user']['user_name'];
            $item['latest_note'] = $item['latest_note']['note'];
        } else {
            $item['latest_note_user'] = "";
            $item['latest_note'] = "";
        }
        return $item;
    });
    return $collection;
});

$collection = $transform($collection);

$csv = Writer::createFromFileObject(new \SplTempFileObject());
$columnNames = array_keys($collection->values()->toArray()[0]);
$csv->insertOne($columnNames);
$collection->each(function ($item) use ($csv) {
    error_log(print_r($item->toArray(), true));
    // Error here, because $item->toArray() still contains array values
    $csv->insertOne($item->toArray());
});

sample_input_collection

Array
(
    [id] => 3
    [first_name] => Alex
    [last_name] => Weissman
    [email] => [email protected]
    [institution_id] => 3
    [academic_level] => Undergraduate
    [courses] => all of them
    [taken] => nope
    [experience] => dunno
    [great] => dunno
    [addl] => dunno
    [status_id] => 2
    [created_at] => 2016-06-06 12:16:40
    [updated_at] => 2016-06-07 14:42:55
    [activity] => 2016-06-07 14:39:40
    [institution] => Array
        (
            [id] => 3
            [name] => University of Maryland College Park
        )

    [status] => Array
        (
            [id] => 2
            [status] => pending interview
        )

    [latest_note] => Array
        (
            [id] => 41
            [user_id] => 1
            [application_id] => 3
            [note] => something boring I guess
            [type] => note
            [created_at] => 2016-06-07 14:39:40
            [updated_at] => 2016-06-07 14:39:40
            [user] => Array
                (
                    [id] => 1
                    [user_name] => root
                )

        )

)