[support] question about jquery selectboxes plugin

I'm creating a select box dynamically from JSON data, and setting up a selected value in URL, but I have a problem.

http://...../gallery/2

My php code: $selected = arg(1);

if ( $selected ) { drupal_add_js('var url_class = '. $selected, 'inline'); }

My javascript code:

$('#class-filter').addOption({'0':' -- ALL -- '},false); $('#class-filter').ajaxAddOption(Drupal.settings.basePath + 'gallery/class',{},true, my_selectOption);

function my_selectOption(){ $(this).selectOptions( '' + url_class + '', true ); }

var classification = $('#gallery-classification-filter').val();

The select box is created OK, and the value showed as selected is == url_class, but the value of the object still is 0.

The question:

Why classification value == 0??? must be == url_class!!