File API

Revision as of 22:12, 22 May 2012 by Matt Clarkson (talk | contribs) (Delete file)

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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

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.

In most cases this is done by calling a callback function in the appropriate plugin, these functions are stored in lib.php files and 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.

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) {
    $url = "{$CFG->wwwroot}/pluginfile.php/{$file->get_contextid()}/mod_assignment/submission}";
    $filename = $file->get_filename();
    $fileurl = $url.$file->get_filepath().$file->get_itemid().'/'.$filename;
    $out[] = html_writer::link($fileurl, $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.

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