First you have to select the preference workspace using the addWorkSpace() function:

$core->auth->user_prefs->addWorkSpace('example');

To save a preference, the function put() is used, with the following parameters:

1. preference name (a string containing only digits, characters without accents and _)
2. its value
3. its type (a string) (optional bu recommended to avoid ambiguities)
4. its label (a string) (optional)
5. a boolean: replace the old value (default: yes) (optional)
6. a boolean: the parameter is global (default: no) (optional)

# workspace creation
$core->auth->user_prefs->addWorkSpace('example');
# the $core->auth->user_prefs->example object has been created

# saving the preference in the example workspace
$core->auth->user_prefs->example->put('pref_name', __('Hello World!'), 'string', 'My label');

It is possible to use the assignation by reference to ease the access to preferences:

# workspace creation
$core->auth->user_prefs->addWorkSpace('example');
 
# assigning by reference, $example_prefs points to the newly created workspace
$example_prefs =& $core->auth->user_prefs->example;
 
# saving the preference
$example_prefs->put('pref_name', __('Hello World!'), 'string', 'My label');

Saving a float:

$core->auth->user_prefs->example->put('pi', 3.14159265, 'float');

Saving an integer:

$core->auth->user_prefs->example->put('nb_entries', 217, 'integer');

Saving a boolean:

$core->auth->user_prefs->example->put('is_valid', true, 'boolean');

Saving a string:

$core->auth->user_prefs->example->put('title', __('Hello World!'), 'string');

A preference is assigned to the $core→auth→user_prefs→workspace name→preference name variable, for instance:

$string = $core->auth->user_prefs->example->title;

Use the drop() function with the preference identifier as argument:

$core->auth->user_prefs->addWorkspace('example');
 
# preference creation
$core->auth->user_prefs->example->put('title', __('Hello World!'), 'string');
 
# preference deletion
$core->auth->user_prefs->example->drop('title');