Due to standard symfony's mime guessers doesn't detect proper svg files' mime, there should be some simple way to detect it

AppBundle.php

<?php

namespace AppBundle;

use AppBundle\File\MimeType\SVGMimeTypeGuesser;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesser;
use Symfony\Component\HttpKernel\Bundle\Bundle;

class AppBundle extends Bundle
{
    public function boot() {
        parent::boot();

        MimeTypeGuesser::getInstance()->register(new SVGMimeTypeGuesser());
    }
}

SVGMimeTypeGuesser.php

<?php

namespace AppBundle\File\MimeType;

use Symfony\Component\HttpFoundation\File\Exception\AccessDeniedException;
use Symfony\Component\HttpFoundation\File\Exception\FileNotFoundException;
use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface;

class SVGMimeTypeGuesser implements MimeTypeGuesserInterface {

    private $MIMETYPE_NAMESPACES = array(
        'http://www.w3.org/2000/svg' => 'image/svg+xml'
    );

    /**
     * Returns whether this guesser is supported on the current OS.
     *
     * @return bool
     */
    public static function isSupported()
    {
        return class_exists('DOMDocument') && class_exists('DOMXPath');
    }

    /**
     * Guesses the mime type of the file with the given path.
     *
     * @param string $path The path to the file
     *
     * @return string The mime type or NULL, if none could be guessed
     *
     * @throws FileNotFoundException If the file does not exist
     * @throws AccessDeniedException If the file could not be read
     */
    public function guess($path) {
        if (!is_file($path)) {
            throw new FileNotFoundException($path);
        }

        if (!is_readable($path)) {
            throw new AccessDeniedException($path);
        }

        if (!self::isSupported()) {
            return;
        }

        $dom = new \DOMDocument();
        $xml = $dom->load($path, LIBXML_NOERROR + LIBXML_ERR_FATAL + LIBXML_ERR_NONE);
        if ($xml === false) {
            return;
        }
        $xpath = new \DOMXPath($dom);
        foreach ($xpath->query('namespace::*') as $node) {
            if (isset($this->MIMETYPE_NAMESPACES[$node->nodeValue])) {
                return $this->MIMETYPE_NAMESPACES[$node->nodeValue];
            }
        }
        return;
    }
}