There are two very different hooks you can use, depending on the installation: wpmu_validate_user_signup for multi-site and registration_errors for single-site. The following untested code shows how to use them. You can tweak the array in user_name_is_forbidden() to your needs. Use regular expressions for the matches. // multi-site add_filter( ‘wpmu_validate_user_signup’, function( $result ) { // there … Read more
You can filter ‘wpmu_validate_user_signup’ and check if the error code matches the 4 character warning. Then just unset the error code. Sample plugin: <?php # -*- coding: utf-8 -*- /* Plugin Name: Allow short user names for multi site. */ add_filter( ‘wpmu_validate_user_signup’, ‘wpse_59760_short_user_names’ ); /** * Allow very short user names. * * @wp-hook wpmu_validate_user_signup … Read more
You can use spaces in usernames, no problem. Several users on wordpress.org have spaces in their usernames. Strict mode only allows these characters: a-z0-9<space>_.\-@ However WP doesn’t default to strict mode. Now, multisite has different restrictions, and it may strip spaces there. This is because usernames are used to create independent blogs and such on … Read more
This seems to do what you need. <?php global $current_user; wp_get_current_user(); ?> <?php if ( is_user_logged_in() ) { echo ‘Username: ‘ . $current_user->user_login . “\n”; echo ‘User display name: ‘ . $current_user->display_name . “\n”; } else { wp_loginout(); } ?>