MIME Info

Developers know that the Drupal determines MIME-type of file by extension, but this is not quite the right way. If I'll change an extension of *.php file to *.jpg, then MIME-type will be determined as image/jpeg but, in fact, it will be the application/x-httpd-php. The MIME Info module solves this problem.

Drupal 8

Adds Symfony MIME type guessers to container and allow to have isSupported() method for every guesser.

Usage

Drupal::service('file.mime_type.guesser')->guess($uri);

Drupal 7

Features

The module provides overrides for three basic stream wrappers - public, private and temporary. If you allow the overriding, the MIME-type of files will be determined with help of FileInfo extension, or, if it does not exist, - by binary data.

Also, if you have non-standard stream wrapper, you can use the mimeinfo($uri) function in getMimeType() method or easily override an object by following the instruction:

1. Select available wrapper in Override the stream wrappers section on admin/config/media/file-system page.
2. Add mimeinfo as the dependency to a module that will override a wrapper.
3. Create the class by following the naming convention rules: MimeInfo<WRAPPER>StreamWrapper. If the wrapper name is test-public_fb@files, then class should be named MimeInfoTestPublicFbFilesStreamWrapper.

Note: If you use extended wrappers and try to get the MIME-type of non-existent file, then the method of default object will be used. Due to that, the MIME-type of non-existent file may differ.

Example of overriding the "Remote" stream wrapper

class MimeInfoRemoteStreamWrapper extends DrupalPublicStreamWrapper {

  /**
   * {@inheritdoc}
   */
  public static function getMimeType($uri, $mapping = NULL) {
    return mimeinfo($uri) ?: parent::getMimeType($uri, $mapping);
  }

}

Known issues

1. If your PHP version is greater than 5.4 then you'll get a warning message that the stream_cast method is not implemented by Drupal.