WordPress at a glance
function is not described

upgrade_400() WP 4.0.0

Execute changes made in WordPress 4.0.0.

  • Global. Int. $wp_current_db_version

No Hooks.

Return

Nothing (null).

Usage

upgrade_400();

Code of upgrade 400: wp-admin/includes/upgrade.php VER 5.1.1

<?php
function upgrade_400() {
	global $wp_current_db_version;
	if ( $wp_current_db_version < 29630 ) {
		if ( ! is_multisite() && false === get_option( 'WPLANG' ) ) {
			if ( defined( 'WPLANG' ) && ( '' !== WPLANG ) && in_array( WPLANG, get_available_languages() ) ) {
				update_option( 'WPLANG', WPLANG );
			} else {
				update_option( 'WPLANG', '' );
			}
		}
	}
}