wp_dropdown_categories.php

$args = array(
        'show_option_all'    => __( 'Select a category', 'inmyarea' ),
        //'show_option_none'   => '',
        //'option_none_value'  => '-1',
        'orderby'            => 'name',
        'order'              => 'ASC',
        'hide_empty'         => 1,
        'selected'           => $cat,
        'hierarchical'       => 1,
        'name'               => 'browse',
        'id'                 => 'browse',
        'class'              => 'browse',
        'taxonomy'           => 'category',
        'hide_if_empty'      => false,
        'value_field'	     => 'term_id',
);
wp_dropdown_categories( $args );