What is wp_insert_term "alias_of" arg for?

Question

I currently put my hands into WP taxonomy and terms to find solutions for my project. I knew that it's not possible to have same terms slug when creating a term with wp_insert_term in one Custom Taxonomy and between different Custom Taxonomies, but i would like to have different terms linked to the same url (so slugs are involved in it) and get all the related posts to these different terms.

Say a custom Taxonomy 'tax' and the following terms in it :

a (slug : a) 
--b (slug : b)
-c (slug : c)
---d (slug : d)

I can access the different tax term with the following links :

/tax/a
/tax/b
/tax/c
/tax/d

If i want to insert a term with wp_insert_term('e','tax',array(slug=>'a'), WP will modify the slug to 'a1' because slugs should be unique...

So, seems impossible to redirect different terms to the same slug/url and get all the custom posts from 'a' and 'e'.

And what about alias_of argument ? Can't find any full documentation about it . Wasn't it precisely for that kind of issue ? I've inserted several terms with that kind of code : wp_insert_term('e','tax',array(slug=>'e','alias_of'=>'a') but it doesn't change anything, WP creates different unique slugs for all my entries and doesn't care about alias_of.

Is Anybody here can clarify this or have a solution ?

thanks a lot !

EDIT

Seems to be related to term_group , a feature that isn't really yet supported by WP. There is a term_group field in wp_terms database . The value of this field is set on term creation wp_insert_term($name,$taxonomy,array('alias_of' => $slug) and retrieve when get a term with (for ex get_term_by()->term_group function). There should be a way to query this but with the terms metas support, i don't really see the interest ...

Answer 1

In the Code Reference it says:

'alias_of'

(string) Slug of the term to make this term an alias of. Default empty string. Accepts a term slug.

This makes a term an alias of another term. Using your example this is how you would use it:

wp_insert_term( 'e', 'tax', array( 'alias_of' => 'a' ) );

This would create a new term e in the tax taxonomy without its own slug, and posts in e would also show up under the a slug.