<?php
global $wpdb;

$iclsettings                      = get_option( 'icl_sitepress_settings' );
$iclsettings['remember_language'] = 24;

update_option( 'icl_sitepress_settings', $iclsettings );
$wpdb->update( $wpdb->prefix . 'icl_languages', array( 'default_locale' => 'it_IT' ), array( 'code' => 'it' ) );