WordPress Portfolio Tags Taxonomy

add_action( 'init', 'wpex_portfolio_tag_tax' );
function wpex_portfolio_tag_tax() {

    //portfolio tag tax labels
    $wpex_portfolio_tag_labels = array(
        'name' => __( 'Portfolio Tags', 'wpex' ),
        'singular_name' => __( 'Portfolio Tag', 'wpex' ),
        'search_items' =>  __( 'Search Portfolio Tags', 'wpex' ),
        'all_items' => __( 'All Portfolio Tags', 'wpex' ),
        'parent_item' => __( 'Parent Portfolio Tag', 'wpex' ),
        'parent_item_colon' => __( 'Parent Portfolio Tag:', 'wpex' ),
        'edit_item' => __( 'Edit Portfolio Tag', 'wpex' ),
        'update_item' => __( 'Update Portfolio Tag', 'wpex' ),
        'add_new_item' => __( 'Add New Portfolio Tag', 'wpex' ),
        'new_item_name' => __( 'New Portfolio Tag Name', 'wpex' ),
        'choose_from_most_used' => __( 'Choose from the most used portfolio categories', 'wpex' )
    );


    //register portfolio tag tax
    register_taxonomy('portfolio_tag','portfolio',array(
        'hierarchical' => true,
        'labels' => apply_filters('wpex_portfolio_tax_labels', $wpex_portfolio_tag_labels),
        'query_var' => true,
        'rewrite' => array( 'slug' => 'portfolio-category' ),
    ));

}