Change the user_login at registration

Question

I use a third party plugin that adds Social Login option to my blog. It works very well, but I dislike that when users choose to login by their social accounts the user login names (user_login in database) are saved in this format - "First-Second", so the first letter of the each part are capitals. My own user_login will be "Iurie-Malai", but I would like "iurie-malai".

I know that WordPress usernames are case-insensitive, but I want that user logins to be only in lowercase. How can I do this?

Answer 1

You can hook into the user_register action hook and lower case the strings manually, by using the wp_update_user function. Here's a quick example:

add_action( 'user_register', 'callback_function', 10, 1 );

function callback_function( $user_id ) {
    // Get the user by their ID
    $user = get_user_by( 'id', $user_id );
    // Update their user_login
    wp_update_user(
        array( 
            'ID'         => $user_id, 
            'user_login' => strtolower( $user->user_login ) 
        )
    );
}

Using the pre_user_login filter

You can use the above filter to filter the user's login before its added to the database, as follows:

add_filter( 'pre_user_login', 'callback_function' );
function callback_function( $login ) {
    return strtolower( $login );
}