File API

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Moodle 2.0


Overview

The File API is for managing all the files stored by Moodle. If you are interested in how the file API works internally, see File API internals. The page is just about what you need to know to use the file API. Related is the Repository API, which lets users get files into Moodle.

If you are looking for an explanation on how to manage moodle files in moodle forms, you most likely need to read Using the File API in Moodle forms.

File areas

Files are conceptually stored in file areas. A file area is uniquely identified by:

  • A context id.
  • full component name (using Frankenstyle), for example 'course', 'mod_forum', 'mod_glossary', 'block_html'.
  • A file area type, for example 'intro' or 'post'.
  • A unique itemid. Normally, the itemid relates to something depending on the file area type. For example, for a 'course', 'intro' file area, the itemid is 0. For forum post, it is the post id.

File areas are not listed separately anywhere, they are stored implicitly in the files table. Please note that each subsystem is allowed to access only own file areas, for example only code in /mod/assignment/* may access files with component 'mod_assignment'.

Naming file areas

The names of the file areas are not strictly defined, but it is strongly recommended to use singulars and common names of areas if possible (intro, post, attachment, description, ...).

Serving files to users

You must refer to the file with a URL that includes a file-serving script, often pluginfile.php. For example

The general form of the URL is something like

$url = $CFG->wwwroot/pluginfile.php/$contextid/$component/$filearea/arbitrary/extra/infomation.ext

A specific example might be

$url = $CFG->wwwroot/pluginfile.php/$forumcontextid/mod_forum/post/$postid/image.jpg

Usually, you do not need to construct this URL directly - the function moodle_url::make_pluginfile_url() should be used instead:

$url = moodle_url::make_pluginfile_url($file->get_contextid(), $file->get_component(), $file->get_filearea(), $file->get_itemid(), $file->get_filepath(), $file->get_filename());

Note: If you do not need the 'itemid', then pass null in as this parameter and it will be entirely missed out from the URL - you need to take this into account when serving the file in the callback function, below.

The file serving script then looks at the context id, and component name, and the file area name, and based on that arranges for the file to be served, following appropriate security checks.

Note: In most cases, when developing third party plugins, pluginfile.php looks for a callback function in the appropriate plugin. These functions are stored in lib.php files and are named component_name_pluginfile(). The arbitrary/extra/infomation.ext is passed to the callback. For example, files in the mod_forum+post file area end up being served by the mod_forum_pluginfile function in mod/forum/lib.php. This function in MYPLUGIN/lib.php will usually follow a pattern like the example below, but the details will vary depending on the restrictions your plugin places on accessing different files (e.g. assignment files can only be accessed by teachers and the student who submitted the file, forum attachments require access to the discussion they are posted on):

function MYPLUGIN_pluginfile($course, $cm, $context, $filearea, $args, $forcedownload, array $options=array()) {
// Check the contextlevel is as expected - if your plugin is a block, this becomes CONTEXT_BLOCK, etc.
if ($context->contextlevel != CONTEXT_MODULE) {
return false;
}
 
// Make sure the filearea is one of those used by the plugin.
if ($filearea !== 'expectedfilearea' && $filearea !== 'anotherexpectedfilearea') {
return false;
}
 
// Make sure the user is logged in and has access to the module (plugins that are not course modules should leave out the 'cm' part).
require_login($course, true, $cm);
 
// Check the relevant capabilities - these may vary depending on the filearea being accessed.
if (!has_capability('mod/MYPLUGIN:view', $context)) {
return false;
}
 
// Leave this line out if you set the itemid to null in make_pluginfile_url (set $itemid to 0 instead).
$itemid = array_shift($args); // The first item in the $args array.
 
// Use the itemid to retrieve any relevant data records and perform any security checks to see if the
// user really does have access to the file in question.
 
// Extract the filename / filepath from the $args array.
$filename = array_pop($args); // The last item in the $args array.
if (!$args) {
$filepath = '/'; // $args is empty => the path is '/'
} else {
$filepath = '/'.implode('/', $args).'/'; // $args contains elements of the filepath
}
 
// Retrieve the file from the Files API.
$fs = get_file_storage();
$file = $fs->get_file($context->id, 'mod_MYPLUGIN', $filearea, $itemid, $filepath, $filename);
if (!$file) {
return false; // The file does not exist.
}
 
// We can now send the file back to the browser - in this case with a cache lifetime of 1 day and no filtering.
// From Moodle 2.3, use send_stored_file instead.
send_file($file, 86400, 0, $forcedownload, $options);
}

You normally use an API function to generate these URL automatically, most often the file_rewrite_pluginfile_urls function.

Getting files from the user

Examples

Please note that in reality developers outside of core will not deal with file api directly in majority of cases, instead use formslib elements which are doing all this automatically.

Browsing files

$browser = get_file_browser();
$context = get_system_context();
 
$filearea = null;
$itemid = null;
$filename = null;
if ($fileinfo = $browser->get_file_info($context, $component, $filearea, $itemid, '/', $filename)) {
// build a Breadcrumb trail
$level = $fileinfo->get_parent();
while ($level) {
$path[] = array('name'=>$level->get_visible_name());
$level = $level->get_parent();
}
$path = array_reverse($path);
$children = $fileinfo->get_children();
foreach ($children as $child) {
if ($child->is_directory()) {
echo $child->get_visible_name();
// display contextid, itemid, component, filepath and filename
var_dump($child->get_params());
}
}
}

Moving files around

For example, if you have just built a file at the path

$from_zip_file = $CFG->dataroot . '/temp/backup/' . $preferences->backup_unique_code .
'/' . $preferences->backup_name;

And you want to move it into the course_backup file area, do

$context = get_context_instance(CONTEXT_COURSE, $preferences->backup_course);
$fs = get_file_storage();
$file_record = array('contextid'=>$context->id, 'component'=>'course', 'filearea'=>'backup',
'itemid'=>0, 'filepath'=>'/', 'filename'=>$preferences->backup_name,
'timecreated'=>time(), 'timemodified'=>time());
$fs->create_file_from_pathname($file_record, $from_zip_file);

List area files

$fs = get_file_storage();
$files = $fs->get_area_files($contextid, 'mod_assignment', 'submission', $submission->id);
foreach ($files as $f) {
// $f is an instance of stored_file
echo $f->get_filename();
}

Or as links...

$out = array();
 
$fs = get_file_storage();
$files = $fs->get_area_files($contextid, 'mod_assignment', 'submission', $submission->id);
 
foreach ($files as $file) {
$filename = $file->get_filename();
$url = moodle_url::make_file_url('/pluginfile.php', array($file->get_contextid(), 'mod_assignment', 'submission',
$file->get_itemid(), $file->get_filepath(), $filename));
$out[] = html_writer::link($url, $filename);
}
$br = html_writer::empty_tag('br');
 
return implode($br, $out);

Create file

Here's how to create a file whose contents will be a text string. This is the equivalent of the PHP function file_put_contents.

$fs = get_file_storage();
 
// Prepare file record object
$fileinfo = array(
'contextid' => $context->id, // ID of context
'component' => 'mod_mymodule', // usually = table name
'filearea' => 'myarea', // usually = table name
'itemid' => 0, // usually = ID of row in table
'filepath' => '/', // any path beginning and ending in /
'filename' => 'myfile.txt'); // any filename
 
// Create file containing text 'hello world'
$fs->create_file_from_string($fileinfo, 'hello world');

If you want to create a file in the Moodle file area based on a 'real' file e.g. in a temporary folder, you can use create_file_from_pathname instead. Similarly, you can create a file based on some other file already in Moodle's local files by using create_file_from_storedfile. Browse through lib/filestorage/file_storage.php for details.

Unlike with ordinary files, this method will not automatically overwrite an existing file. If you wish to overwrite a file, you must first get the file and (if it exists) delete it, and only then create it again.

Read file

This is a way to read a file, equivalent to file_get_contents. Please note your are allowed to do this ONLY from mod/mymodule/* code, it is not acceptable to do this anywhere else. Other code has to use file_browser interface instead.

$fs = get_file_storage();
 
// Prepare file record object
$fileinfo = array(
'component' => 'mod_mymodule', // usually = table name
'filearea' => 'myarea', // usually = table name
'itemid' => 0, // usually = ID of row in table
'contextid' => $context->id, // ID of context
'filepath' => '/', // any path beginning and ending in /
'filename' => 'myfile.txt'); // any filename
 
// Get file
$file = $fs->get_file($fileinfo['contextid'], $fileinfo['component'], $fileinfo['filearea'],
$fileinfo['itemid'], $fileinfo['filepath'], $fileinfo['filename']);
 
// Read contents
if ($file) {
$contents = $file->get_content();
} else {
// file doesn't exist - do something
}

If you want to access the file directly on disk, this is not permitted. Instead, you need to make a copy of the file in a temporary area and use that. You can do this with $file->copy_content_to($pathname).

Delete file

$fs = get_file_storage();
 
// Prepare file record object
$fileinfo = array(
'component' => 'mod_mymodule',
'filearea' => 'myarea', // usually = table name
'itemid' => 0, // usually = ID of row in table
'contextid' => $context->id, // ID of context
'filepath' => '/', // any path beginning and ending in /
'filename' => 'myfile.txt'); // any filename
 
// Get file
$file = $fs->get_file($fileinfo['contextid'], $fileinfo['component'], $fileinfo['filearea'],
$fileinfo['itemid'], $fileinfo['filepath'], $fileinfo['filename']);
 
// Delete it if it exists
if ($file) {
$file->delete();
}

See also