File System



Elgg’s filestore is located in the site’s dataroot that is configured during installation, and can be modified via site settings in Admin interface.

Directory Structure

The structure of the filestore is tied to file ownership by Elgg entities. Whenever the first file owned by an entity is written to the filestore, a directory corresponding to the entity GUID will be created within a parent bucket directory (buckets are bound to 5000 guids). E.g. files owned by user with guid 7777 will be located in 5000/7777/.

When files are created, filenames can contain subdirectory names (often referred to as $prefix throughout the code). For instance, avatars of the above user, can be found under 5000/7777/profile/.

File Objects

Writing Files

To write a file to the filestore, you would use an instance of ElggFile. Even though ElggFile extends ElggObject and can be stored as an actual Elgg entity, that is not always necessary (e.g. when writing thumbs of an image).

$file = new ElggFile();
$file->owner_guid = 7777;
$file->write('Contents of the file');

// to uprade this file to an entity
$file->subtype = 'file';

Reading Files

You can read file contents using instanceof of ElggFile.

// from an Elgg entity
$file = get_entity($file_guid);
// arbitrary file on the filestore
$file = new ElggFile();
$file->owner_guid = 7777;

// option 1
$contents = $file->grabFile();

// option 2
$contents = file_get_contents($file->getFilenameOnFilestore());

Serving Files

You can serve files from filestore using elgg_get_inline_url() and elgg_get_download_url(). Both functions accept 3 arguments:

  • ``file`` An instance of ElggFile to be served
  • ``use_cookie`` If set to true, validity of the URL will be limited to current session
  • ``expires`` Expiration time of the URL

You can use use_cookie and expires arguments as means of access control. For example, users avatars in most cases have a long expiration time and do not need to be restricted by current session - this will allows browsers to cache the images and file service will send appropriate Not Modified headers on consecutive requests.

For entities that are under Elgg’s access control, you may want to use cookies to ensure that access settings are respected and users do not share download URLs with somebody else.

You can also invalidated all previously generated URLs by updating file’s modified time, e.g. by using touch().

Embedding Files

Please note that due to their nature inline and download URLs are not suitable for embedding. Embed URLs must be permanent, whereas inline and download URLs are volatile (bound to user session and file modification time).

To embed an entity icon, use elgg_get_embed_url().