Symfony2 - checking if file exists

Question

I have a loop in Twig template, which returns multiple values. Most important - an ID of my entry. When I didn\'t use any framework nor template engine, I used simply

Answer 1

Here is my solution, using SF4, autowire and autoconfigure:

namespace App\Twig;

use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;
use Symfony\Component\Filesystem\Filesystem;

class FileExistsExtension extends AbstractExtension
{
    private $fileSystem;
    private $projectDir;

    public function __construct(Filesystem $fileSystem, string $projectDir)
    {
        $this->fileSystem = $fileSystem;
        $this->projectDir = $projectDir;
    }

    public function getFunctions(): array
    {
        return [
            new TwigFunction('file_exists', [$this, 'fileExists']),
        ];
    }

    /**
     * @param string An absolute or relative to public folder path
     * 
     * @return bool True if file exists, false otherwise
     */
    public function fileExists(string $path): bool
    {
        if (!$this->fileSystem->isAbsolutePath($path)) {
            $path = "{$this->projectDir}/public/{$path}";
        }

        return $this->fileSystem->exists($path);
    }
}

In services.yaml:

services:
    App\Twig\FileExistsExtension:
        $projectDir: '%kernel.project_dir%'

In templates:

# Absolute path
{% if file_exists('/tmp') %}
# Relative to public folder path
{% if file_exists('tmp') %}

I am new to Symfony so every comments are welcome!

Also, as initial question is about Symfony 2, maybe my answer is not relevant and I would better ask a new question and answer by myself?