Local Packages

composer.json

{
    "require": {
        "my-packages/http-responses": "*@dev",
    },
    "repositories": [
        {
            "type": "path",
            "url": "./packages/*"
        }
    ]
}

packages__http-responses__composer.json

{
  "name": "my-packages/http-responses",
  "type": "library",
  "description": "Http Responses for Symfony",
  "autoload": {
    "psr-4": { "MyPackages\\HttpResponses\\": "src/" }
  }
}

packages__http-responses__src__CsvResponse.php

<?php

namespace MyPackages\HttpResponses;

use Symfony\Component\HttpFoundation\Response;

class CsvResponse extends Response
{
    /** @var string */
    protected $data;
    /** @var string */
    protected $filename = 'export.csv';

    public function __construct($data = [], $status = 200, $headers = [])
    {
        parent::__construct('', $status, $headers);

        $this->setData($data);
    }

    public function setData($data): self
    {
        $this->data = '';
        $output = fopen('php://temp', 'r+');

        if (0 !== \count($data)) {
            if (array_keys($data[0]) !== range(0, \count($data[0]) - 1)) {
                fputcsv($output, array_keys($data[0]));
            }

            foreach ($data as $row) {
                fputcsv($output, $row);
            }

            rewind($output);
            while ($line = fgets($output)) {
                $this->data .= $line;
            }
        }

        $this->data .= fgets($output);

        return $this->update();
    }

    public function getFilename(): string
    {
        return $this->filename;
    }

    public function setFilename($filename): self
    {
        $this->filename = $filename;

        return $this->update();
    }

    protected function update(): self
    {
        $this->headers->set('Content-Disposition', sprintf('attachment; filename="%s"', $this->filename));

        if (!$this->headers->has('Content-Type')) {
            $this->headers->set('Content-Type', 'text/csv');
        }

        return $this->setContent($this->data);
    }
}

__ indicates a subfolder.