Tag API before 3.1

Moodle 2.0

Tag API overview

The Tag API allows you to assign labels to information in Moodle. This makes finding this information easier and also facilitates the grouping of similar information. The Tag API allows you to create, modify, delete and search tags in the Moodle system. The main tag related functions can be found in the tag/lib.php and tab/locallib.php files. For a through overview of all of the functions available for working with Tags please see SYSTEM X, however the following examples should give you a general understanding of how to get started with tags.

Tag API Usage

Tags associate a value with an instance of a type of item. In that sense tags are generic, but they can be put to specific uses by creative plugin developers, for example:

• adding tag values to an instance of a forum post;
• adding tag values to an instance of a blog;
• adding tag values to a specific user's profile; or
• associating tag values with specific instances of any identifiable item.

The follow examples work with tags associated with a specific user for their profile. The examples form a series however the calls demonstrated could happen in isolation. If you read these examples in sequence, you should gain an understanding of the Tag API.

Remove tags

Suppose we want to remove all tags associated with a user.

require_once($CFG->dirroot.'/tag/locallib.php');

// Lets pretend we want to update the tags for a user who has an ID of 9969959299 $userId = 9969959299;

tag_set('user', $userId, array()); // Delete all user->$userId tags by passing an empty array tag_get_tags('user', $userId); // returns an empty array()

Add a tag

Now suppose we want to add 'chess' to the list of tags for the given user.

tag_set_add('user', $userId, 'chess'); // Add chess to the list of tags for user->$userId tag_get_tags('user', $userId); /* returns: Array (

   [14] => stdClass Object
       (
           [id] => 14
           [tagtype] => default
           [name] => chess
           [rawname] => chess
           [flag] => 0
           [ordering] => 0
       )

)

• /

Delete a tag

Suppose we want to delete the newly created chess tag.

tag_set_delete('user', $userId, 'chess'); //Delete the chess tag for user->$userId tag_get_tags('user', $userId); // returns an empty array()

Adding a number of tags at once

We could now add 'table tennis', 'foosball' and 'programming' as tags for the given user in a single call.

tag_set('user', $userId, array('table tennis', 'foosball', 'programming')); //Add some more tags for user->$userId

Get tags

We may want to check all tags associated with the given user.

$tags = tag_get_tags('user', $userId); /* $tags value is: Array (

   [15] => stdClass Object
       (
           [id] => 15
           [tagtype] => official
           [name] => table tennis
           [rawname] => table tennis
           [flag] => 0
           [ordering] => 0
       )

   [16] => stdClass Object
       (
           [id] => 16
           [tagtype] => default
           [name] => foosball
           [rawname] => foosball
           [flag] => 0
           [ordering] => 1
       )

   [17] => stdClass Object
       (
           [id] => 17
           [tagtype] => default
           [name] => programming
           [rawname] => programming
           [flag] => 0
           [ordering] => 2
       )

)

• /

Make a tag official

We could make the first element from the last example (the table tennis tag) an official tag.

$firstTagKey = key($tags); // Grab the first key (which happens to be the key for table tennis). if($firstTagKey) {

   tag_type_set($firstTagKey, 'official'); // Make table tennis an official tag

Get official tags

We can output official tags for the given user.

tag_get_tags('user', $userId, 'official'); /* Returns: Array (

   [15] => stdClass Object
       (
           [id] => 15
           [tagtype] => official
           [name] => table tennis
           [rawname] => table tennis
           [flag] => 0
           [ordering] => 0
       )

)

• /

Set a description

We could now set a description for the table tennis tag.

tag_description_set($firstTagKey, '

Another name for wiff-waff"

', FORMAT_HTML);

Get details of a specific tag

We can get the details of the table tennis tag.

The last parameter is a filter which allows you to specify with fields you wish to have returned. Setting it to an asterisk acts as a wildcard and returns everything.

tag_get('name', 'table tennis', '*'); /* Returns: stdClass Object (

   [id] => 15
   [userid] => 2
   [name] => table tennis
   [rawname] => table tennis
   [tagtype] => official

[description] =>

Another name for wiff-waff"

   [descriptionformat] => 1
   [flag] => 0
   [timemodified] => 1327343334

)

• /

Output a tag clout

We can output a tag cloud for all tags in the system.

tag_print_cloud();

Tag API database tables

Tag

This table holds all of the tags which are currently available in the system.

Field	Type	Default	Info
id	int(10)	auto-incrementing	The unique ID for this Tag.
userid	int(10)		The user that the Tag belongs to
name	varchar(255)	null	The name of the tag
rawname	varchar(255)		A version of the name which has been normalised with functions such as clean_param and strtolower
tagtype	varchar(255) NULL	null	Specifies the type of the tag. Currently there are only two types of tags, official and default. Official is used for tags that have been accepted by administrators.
description	text NULL		A description of the tag. It's format is specified by the descriptionformat field of this table
descriptionformat	tinyint(2) unsigned	0	Specifies the MOODLE TEXT format of the description (see: https://docs.moodle.org/dev/Text_formats_2.0#Database_structure)
flag	smallint(4)	0	Used to identify tags that have been marked as inappropriate
timemodified	bigint(10)		The time that the tag was last updated.

Tag_Instance

This table is use to record the instances of each tag's use. It has a many to one relationship with the tag table shown above.

Field	Type	Default	Info
id	int(10)	auto-incrementing	The unique ID for this tag instance
tagid	int(10)		The foreign key which relates to the primary tagid key in the tag table
itemtype	varchar(255)	null	The category that the tag belongs to (eg. user, course)
itemid	int(10)		The ID of the particular item you are linking to. So for an itemtype of user you would use the user's ID for the itemid.
tiuserid	int(10)	0	The userid of the user who created the tag instance.
ordering	int(10)		See http://tracker.moodle.org/browse/MDL-31150
timemodified	int(10)	0	The time that the tag instace was last updated.

See also

• Core APIs