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

Improving on Sybio's answer, Twig_simple_function did not exist for my version and nothing here works for external images for example. So my File extension file is like this:

namespace AppBundle\Twig\Extension;

class FileExtension extends \Twig_Extension
{
/**
 * {@inheritdoc}
 */

public function getName()
{
    return 'file';
}

public function getFunctions()
{
    return array(
        new \Twig_Function('checkUrl', array($this, 'checkUrl')),
    );
}

public function checkUrl($url)
{
    $headers=get_headers($url);
    return stripos($headers[0], "200 OK")?true:false;
}