Tag API before 3.1
This API has been significantly changed in Moodle 3.1. Please see Tag API
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, '<p>Another name for <strong><em>wiff-waff"</em></strong></p>', 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] => <p>Another name for <strong><em>wiff-waff"</em></strong></p>
[descriptionformat] => 1
[flag] => 0
[timemodified] => 1327343334
)
*/
Output a tag cloud
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. |