Wordpress Validate New Nicename/Slug - wordpress

Question

I have written a custom "Edit Account" script that allows a Wordpress user to update their Wordpress account. Everything is working great, except that I can't seem to find a way to update the user's nicename, which also doubles as the user's URL slug (via the get_author_posts_url function). This is causing issues because when a user changes their name, their slug still contains their original name - not the new one.
I know that the sanitize_title function will generate the new nicename, but I don't know how to verify that it is unique and modify it if it is not before entering it into the DB. I am wondering what built-in functions Wordpress has to handle this. I know I can write my own script to do this, but I would much rather use Wordpress functions. I couldn't find this anywhere in the WP documentation. Thanks!

Answer 1

Here is a function I have written to in lue of a built in function:
function new_user_slug($string){
//GENERATE NEW SLUG
$slug=sanitize_title($string);
//MAKE SURE SLUG IS UNIQUE
$result=mysql_query("SELECT * FROM wp_users WHERE user_nicename='$slug'");
if(mysql_num_rows($result)==0){
return $slug;
}else{
$counter=2;
$kill=0;
while($kill==0){
$mod_slug=$slug."-".$counter;
$result=mysql_query("SELECT * FROM wp_users WHERE user_nicename='$mod_slug'");
if(mysql_num_rows($result)==0){
$kill=1;
}else{
$counter++;
}
}
return $mod_slug;
}
}
This takes a string (the user's updated name) and converts it into the default slug. It then checks the slug against the database to see if it is unique. If it is, the slug is returned. If not, it enters an iteration loop that incrementally changes the slug until it is unique.

Answer 2

Try this:
wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_parent )
Source: https://codex.wordpress.org/Function_Reference/wp_unique_post_slug

Answer 3

Actually if you use wordpress user functions like wp_insert_user and wp_update_user Wordpress itselt handles duplicate user_nicename entries and adds -n suffix to them.
So your code would be something like this:
function new_nicename( $user_id, $nicename ) {
$nicename = sanitize_title( $nicename );
$user_id = wp_update_user( array( 'ID' => $user_id, 'user_nicename' => $nicename ) );
}